CN113865518B - Astronomical detection method for included angle between focal plane of large-view-field telescope and CCD target surface - Google Patents
Astronomical detection method for included angle between focal plane of large-view-field telescope and CCD target surface Download PDFInfo
- Publication number
- CN113865518B CN113865518B CN202111173582.XA CN202111173582A CN113865518B CN 113865518 B CN113865518 B CN 113865518B CN 202111173582 A CN202111173582 A CN 202111173582A CN 113865518 B CN113865518 B CN 113865518B
- Authority
- CN
- China
- Prior art keywords
- telescope
- ccd
- focal
- focal length
- focal plane
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000001514 detection method Methods 0.000 title claims abstract description 13
- 230000003287 optical effect Effects 0.000 claims abstract description 29
- 238000000034 method Methods 0.000 claims description 7
- 238000013519 translation Methods 0.000 claims description 4
- 238000005259 measurement Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000003384 imaging method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000004807 localization Effects 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000004806 packaging method and process Methods 0.000 description 1
- 238000005375 photometry Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/26—Measuring arrangements characterised by the use of optical techniques for measuring angles or tapers; for testing the alignment of axes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
- Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Telescopes (AREA)
Abstract
The invention provides an astronomical detection method for the included angle between the focal plane of a large-view-field telescope and the CCD target surface, which can accurately measure the inclination degree of the CCD target surface and the optical focal plane, and then correct the inclination degree by using a gasket with standard size at the mounting flange of the CCD camera and the optical telescope, thereby solving the problem that the star image is virtual and real in astronomical observation.
Description
Technical Field
The invention belongs to the technical field of optical detection, and particularly relates to an astronomical detection method for an included angle between a focal plane of a large-view-field telescope and a CCD target surface.
Background
The CCD has been developed in the 70 s of the 20 th century, can convert optical signals into electric signals, can store and transfer charges, and is widely applied to the field of photoelectric detection, in particular astronomy. With the development of the large-field-of-view night telescope, the requirements of a large-target-surface CCD (pixel 2048x2048 above) camera are increasing. However, due to the influence of factors such as CCD mechanical packaging errors, CCD camera and telescope mounting flange mechanical errors, an included angle exists between the CCD target surface and the telescope optical focal plane, and particularly for a telescope with a large field of view, the focal length is short, the field of view is large, the focal depth is usually smaller than tens of micrometers, and the included angle error hardly reaches the focal depth requirement of an optical system, so that the imaging quality of the CCD full-field star image is influenced. Therefore, it is necessary to detect and correct the angle between the CCD target surface and the focal plane of the optical system.
Disclosure of Invention
The invention aims to solve the technical problems and provides an astronomical detection method for the included angle between the focal plane of a large-view-field telescope and the CCD target surface.
In order to achieve the above purpose, the invention adopts the following technical scheme:
an astronomical detection method for the included angle between the focal plane of a large-view-field telescope and a CCD target surface comprises the following steps:
s1, taking an optical focal plane of an optical telescope as a reference, translating a CCD along the optical axis direction through a telescope focusing system, moving from outside to inside of the focus, or moving from inside to outside of the focus, wherein the translation step length is close to the focal depth length of the telescope, aligning the optical telescope to a dense star field in the CCD translation process, and selecting a proper exposure time to shoot an image;
s2, measuring full width half maximum FWHM of all star images in the image by using an astronomical method, and equally dividing the image into n 2 The average value of the full width half maximum FWHM of the star image in each sky region is counted respectively to obtain n 2 FWHM of the individual antenna field;
s3, along with the movement of the focal length of the telescope, any one of the sky areas passes through the optical focal plane of the telescope, at the moment, the corresponding FWHM is minimum, because the focal length of the telescope and the corresponding FWHM are a group of discrete number columns, in order to obtain the accurate focal length value of a certain day area, the focal length of the telescope is taken as an abscissa, the FWHM is taken as an ordinate to carry out quadratic polynomial fitting, and the focal length value corresponding to the smallest FWHM is the optimal focal length of the certain day area;
s4, after the optimal focal length of all the sky areas is obtained, taking CCD pixel coordinates as x coordinates and y coordinates, taking the optimal focal length as z coordinates, and performing plane fitting to obtain a fitting plane equation, wherein the included angle between the fitting plane and the x and y coordinate planes is the included angle between the CCD target surface and the telescope focal plane.
In a preferred technical scheme, in S1, a focal depth length of the telescope with a step length of the CCD translating along an optical axis direction of the optical telescope being close is Δδ=4λ (f/D) 2, where λ is a wavelength, f is a focal length of the optical system, and D is a primary mirror caliber.
As a preferable technical scheme, in S4, an included angle between the CCD target surface and the focal plane of the telescope is:wherein Zmax is the maximum focal length, zmin is the minimum focal length, a is the number of CCD single-axis pixels, and b is the CCD pixel size in mu m.
After the technical scheme is adopted, the invention has the following advantages:
according to the invention, the inclination degree of the CCD target surface and the optical focal plane can be accurately measured by an astronomical detection method, and then the CCD target surface and the optical focal plane are corrected by using gaskets with standard sizes at the mounting flange of the CCD camera and the optical telescope, so that the problem that the star image is virtual and real in astronomical observation is solved. The invention solves the problem that the included angle between the CCD target surface and the focal plane of the telescope cannot be measured by using a direct measurement method, and can avoid errors caused by installation by using an astronomical detection method, so that a more accurate measurement result is obtained, and the universality is stronger. At the same time, the method can provide reference for automatic target surface calibration.
Drawings
FIG. 1 is a schematic diagram of the measurement of the angle between the CCD target surface and the telescope focal plane;
FIG. 2 is a plot of fit points for polynomial fitting of the telescope focal length and the fixed star FWHM mean for the same sub-sky region;
FIG. 3 is a plot of fitted points for a plane fit of measured focal length values of a CCD sub-sky region;
FIG. 4 is a schematic view of the structure of the CCD camera and telescope mounting flange face;
FIG. 5 is a plot of the corrected CCD target surface versus the telescope focal plane;
FIG. 6 is a diagram showing the FWHM distribution of the corrected full-field star image of the CCD.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
A primary mirror aperture d=1m of a reflective primary focus telescope, whose optical system focal length f=2200 mm, and corresponding focal depth at wavelength λ=650 nm:
therefore, in the range of 0.013mm, the imaging quality can meet the performance requirements of the optical system.
The CCD is a scientific chip, the size of the pixel is 15 mu m, the corresponding pixel scale is 1.4', the CCD field of view is 1.6 DEG x1.6 DEG, which is larger than the effective field of view of the telescope optical system by 1.5 DEG x1.5 DEG, so the CCD edge and the star image quality of four angles are poor.
As shown in fig. 1, the point F is the telescope focal position, and the xFy plane is the telescope focal plane. In the actual measurement process, the telescope is directed to the Galaxy dense star field, so that the full field area is ensured to have enough stars. The focal length of the telescope is adjusted from 1.22mm to 1.92mm in 0.02mm step length, so that the CCD moves from the outside of the telescope focal plane to the inside of the telescope (any area on the CCD needs to pass through the telescope focal plane), 36 images are shot for 20s exposure time each time, and the focal length value (relative to the value of f=2200 mm) of the telescope corresponding to each image is recorded.
First, full field photometry is performed on 36 images, and full width at half maximum (FWHM) values of all stars in each image are obtained. The image 20x20 was aliquoted for 400 sub-day zones and the average of all stars FWHM in each sub-day zone was counted. Then, firstly, performing polynomial fitting for 3 times on the focal length and FWHM mean value of the telescope in the same sub-antenna area in 36 images, and obtaining the lowest point of FWHM as shown in FIG. 2; then, 2 times polynomial fitting is performed on the data points near the lowest point, and the best focus value of the sub-day area is determined. The optimal focal length corresponding to 400 sub-antenna areas can be obtained, the CCD pixel coordinates are taken as x and y (x, y correspond to 0-20), and the optimal focal length of each sub-antenna area is taken as z for mapping. Finally, a plane fit is made to the surface, as shown in fig. 3 for the best focus of 400 sub-fields and the fit plane. Finally, a plane fitting equation is obtained:
z＝0.00008846x+0.00219749y+1.54570968；
from this equation, (x, y) = (0, 0), the focal length z is the smallest; (x, y) = (20, 20), the focal length z is maximum. Therefore, the included angle between the CCD target surface and the telescope focal plane is as follows:
wherein θ is the included angle between the CCD target surface and the telescope focal plane, Z max -Z min =0.045719 mm,4096 is the number of CCD uniaxial pixels, 15 is the CCD pixel size(unit: μm), the angle θ between the CCD target surface and the telescope focal plane was calculated to be 0.03015 °.
WCS information is added to the image by astronomical localization, i.e. both astronomical coordinates (RA, DEC) and pixel coordinates (x, y) are in the image. And judging the corresponding relation between the inclination direction of the CCD target surface and the CCD camera mounting flange surface through the relation between the telescope horizon coordinate and the astronomical coordinate. According to the corresponding relation, according to a fitting plane equation, a standard-size gasket with corresponding thickness is added on the CCD mounting flange surface, so that the CCD target surface is parallel to the focal plane of the telescope, and the thickness of the minimum gasket is 0.02mm as shown in fig. 4.
The same method is used for measuring the included angle between the corrected CCD target surface and the telescope focal plane, and the final result is shown in figure 5. The plane fitting equation is:
z＝-0.00012739x-0.00057248y+1.75676545；
the calculated difference between the maximum focal length and the minimum focal length is Z max -Z min = 0.0139974mm, satisfying telescope depth of focus requirement. The included angle theta between the CCD target surface and the telescope focal plane is 0.00016 degrees.
The statistical distribution of the FWHM of the corrected CCD full-field star image is shown in fig. 6, and the gray scale gradient represents different FWHM values. The star image quality of 80% of the whole field is better than 3", and the astronomical observation requirement is met.
In addition to the above preferred embodiments, the present invention has other embodiments, and various changes and modifications may be made by those skilled in the art without departing from the spirit of the invention, which is defined in the appended claims.
Claims (3)
1. The astronomical detection method for the included angle between the focal plane of the large-view-field telescope and the CCD target surface is characterized by comprising the following steps of:
s1, taking an optical focal plane of an optical telescope as a reference, translating a CCD along the optical axis direction through a telescope focusing system, moving from outside to inside of the focus, or moving from inside to outside of the focus, wherein the translation step length is close to the focal depth length of the telescope, aligning the optical telescope to a dense star field in the CCD translation process, and selecting a proper exposure time to shoot an image;
s2, measuring full width half maximum FWHM of all star images in the image by using an astronomical method, and equally dividing the image into n 2 The average value of the full width half maximum FWHM of the star image in each sky region is counted respectively to obtain n 2 FWHM of the individual antenna field;
s3, along with the movement of the focal length of the telescope, any one of the sky areas passes through the optical focal plane of the telescope, at the moment, the corresponding FWHM is minimum, because the focal length of the telescope and the corresponding FWHM are a group of discrete number columns, in order to obtain the accurate focal length value of a certain day area, the focal length of the telescope is taken as an abscissa, the FWHM is taken as an ordinate to carry out quadratic polynomial fitting, and the focal length value corresponding to the smallest FWHM is the optimal focal length of the certain day area;
and S4, after the optimal focal length of all the sky areas is obtained, taking CCD pixel coordinates as x coordinates and y coordinates, taking the optimal focal length as z coordinates, and performing plane fitting to obtain a fitting plane equation, wherein the included angle between the fitting plane and the x and y coordinate planes is the included angle between the CCD target surface and the telescope focal plane.
2. The astronomical detection method for included angle between focal plane of large-field telescope and target surface of CCD as set forth in claim 1, wherein in S1, focal depth length of telescope where step length of CCD translating along optical axis direction of optical telescope is close is Deltadelta=4λ (f/D), where lambda is wavelength, f is focal length of optical system, and D is caliber of primary mirror.
3. The astronomical detection method for the included angle between the focal plane of the large-view-field telescope and the focal plane of the CCD, as set forth in claim 1, is characterized in that in S4, the included angle between the focal plane of the CCD and the focal plane of the telescope is:wherein Zmax is the maximum focal length, zmin is the minimum focal length, a is the number of single-axis CCD pixels, and b is the size of the CCD pixels in mu m.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111173582.XA CN113865518B (en) | 2021-10-09 | 2021-10-09 | Astronomical detection method for included angle between focal plane of large-view-field telescope and CCD target surface |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111173582.XA CN113865518B (en) | 2021-10-09 | 2021-10-09 | Astronomical detection method for included angle between focal plane of large-view-field telescope and CCD target surface |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113865518A CN113865518A (en) | 2021-12-31 |
| CN113865518B true CN113865518B (en) | 2024-02-06 |
Family
ID=79002188
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111173582.XA Active CN113865518B (en) | 2021-10-09 | 2021-10-09 | Astronomical detection method for included angle between focal plane of large-view-field telescope and CCD target surface |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN113865518B (en) |
Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1037014A2 (en) * | 1999-03-17 | 2000-09-20 | Kabushiki Kaisha Topcon | Electric level |
| CN101975560A (en) * | 2010-11-03 | 2011-02-16 | 中国科学院长春光学精密机械与物理研究所 | Optical detection method for parallelism of planar array CCD target surface and installation locating surface |
| CN102252634A (en) * | 2011-06-16 | 2011-11-23 | 中国科学技术大学 | Laser multiple degrees of freedom precision measurement system based on telescope system |
| CN205427305U (en) * | 2016-02-03 | 2016-08-03 | 中国科学院云南天文台 | Be used for adjusting confocal focusing camera of astronomical telescope system and focusing device thereof |
| CN106203462A (en) * | 2016-06-23 | 2016-12-07 | 中国科学院国家天文台 | Astronomicalc optics transition source quick automatic identification method based on machine learning and system |
| CN108458856A (en) * | 2018-01-04 | 2018-08-28 | 中国科学院国家天文台南京天文光学技术研究所 | The detection device and its method of segmentation detection dome seeing based on laser light source |
| CN110411348A (en) * | 2019-08-28 | 2019-11-05 | 中国人民解放军国防科技大学 | Automatic detection and positioning device and method for laser spot focus |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2835621B1 (en) * | 2002-02-07 | 2004-04-16 | Astrium Sas | OBSERVATION OPTICAL INSTRUMENT FROM A TWO TELESCOPE SATELLITE |
| CN107850769B (en) * | 2014-01-04 | 2020-04-24 | 陈加志 | Automatic astronomical observation system and observation method |
-
2021
- 2021-10-09 CN CN202111173582.XA patent/CN113865518B/en active Active
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1037014A2 (en) * | 1999-03-17 | 2000-09-20 | Kabushiki Kaisha Topcon | Electric level |
| CN101975560A (en) * | 2010-11-03 | 2011-02-16 | 中国科学院长春光学精密机械与物理研究所 | Optical detection method for parallelism of planar array CCD target surface and installation locating surface |
| CN102252634A (en) * | 2011-06-16 | 2011-11-23 | 中国科学技术大学 | Laser multiple degrees of freedom precision measurement system based on telescope system |
| CN205427305U (en) * | 2016-02-03 | 2016-08-03 | 中国科学院云南天文台 | Be used for adjusting confocal focusing camera of astronomical telescope system and focusing device thereof |
| CN106203462A (en) * | 2016-06-23 | 2016-12-07 | 中国科学院国家天文台 | Astronomicalc optics transition source quick automatic identification method based on machine learning and system |
| CN108458856A (en) * | 2018-01-04 | 2018-08-28 | 中国科学院国家天文台南京天文光学技术研究所 | The detection device and its method of segmentation detection dome seeing based on laser light source |
| CN110411348A (en) * | 2019-08-28 | 2019-11-05 | 中国人民解放军国防科技大学 | Automatic detection and positioning device and method for laser spot focus |
Non-Patent Citations (1)
| Title |
|---|
| 黄垒 ; 辛立平 ; 韩旭辉 ; 魏建彦 ; .广角天文望远镜的自动调焦.光学精密工程.2015,(第01期),全文. * |
Also Published As
| Publication number | Publication date |
|---|---|
| CN113865518A (en) | 2021-12-31 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US9686479B2 (en) | Method for combining multiple image fields | |
| CN109903227B (en) | Panoramic image splicing method based on camera geometric position relation | |
| CN108648241B (en) | PTZ camera on-site calibration and focusing method | |
| WO2019100636A1 (en) | Sun-tracking correction system and method based on celestial body image | |
| CN104835159A (en) | Digital image correction method for continuous variable-focal-length optical imaging system | |
| CN107339935B (en) | Target space intersection measuring method for full-view scanning measuring system | |
| CN112634373B (en) | Visual measurement system dynamic correction method based on zero-expansion ceramic calibration plate | |
| CN110047110B (en) | Flexible satellite-borne antenna on-orbit vibration measurement method based on sequence image | |
| CN110501026B (en) | Camera internal orientation element calibration device and method based on array star points | |
| CN110006452A (en) | No. six wide visual field cameras of high score are with respect to geometric calibration method and system | |
| CN113781579B (en) | Geometric calibration method for panoramic infrared camera | |
| Takiguchi et al. | High precision range estimation from an omnidirectional stereo system | |
| CN113865518B (en) | Astronomical detection method for included angle between focal plane of large-view-field telescope and CCD target surface | |
| CN112964238B (en) | Device and method for improving pointing accuracy of optical telescope auxiliary radio telescope | |
| Watanabe et al. | Telecentric optics for constant magnification imaging | |
| CN114860196A (en) | Telescope main light path guide star device and calculation method of guide star offset | |
| CN111796414B (en) | Telescope automatic focusing method based on arc length change between fixed stars | |
| CN101329515B (en) | Device and method for measuring and checking step photoetching machine aligning system | |
| CN108898585B (en) | Shaft part detection method and device | |
| CN113421300B (en) | Method and device for determining actual position of object in fisheye camera image | |
| CN103398782B (en) | A kind of super-resolution thermal infrared imager based on atmospheric turbulence correction | |
| CN114754695A (en) | Multi-view-field bridge deflection measuring device and method and storage medium | |
| CN111044076B (en) | Geometric calibration method for high-resolution first-number B satellite based on reference base map | |
| CN209877942U (en) | Image distance measuring instrument | |
| CN109493382B (en) | Fixed star high-precision position extraction method based on intra-pixel response |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |