The precision of photoelectric tracking and measuring equipment on the vehicle and vessel is deteriorated by the platform’s movement. Specifically, the platform’s movement leads to the deviation or loss of the target, it also causes the jitter of visual axis and then produces image blur. In order to improve the precision of photoelectric equipment, the attitude of photoelectric equipment fixed with the platform must be measured. Currently, laser gyroscope is widely used to measure the attitude of the platform. However, the measurement accuracy of laser gyro is affected by its zero bias, scale factor, installation error and random error. In this paper, these errors were analyzed and compensated based on the laser gyro’s error model. The static and dynamic experiments were carried out on a single axis turntable, and the error model was verified by comparing the gyro’s output with an encoder with an accuracy of 0.1 arc sec. The accuracy of the gyroscope has increased from 7000 arc sec to 5 arc sec for an hour after error compensation. The method used in this paper is suitable for decreasing the laser gyro errors in inertial measurement applications.
In order to study some special solar activities, such as the emergence, evolution and disappearance progress of the sunspot and magnetic flux, and the key role of magnetic field, a new 1.8-meter size high-resolution solar telescope —the CLST will be built in the Institute of Optics and Electronics(IOE), Chinese Academy of Science(CAS), which locates in Chengdu, China. The CLST has a classic Gregorian configuration, alt-azimuth mount, retractable dome. Besides that, a large mechanical de-rotator will be used to cancel the image rotation, and finally it will cooperate with another kind of mechanical de-rotator to cancel both of the pupil rotation and image rotation. Φ3 arc-minute field of view will help the CLST to observe the whole solar activity region, and if necessary the FOV can be enlarged to Φ 6 arc-minute. A 1.8m primary mirror with honeycomb sandwiches structure made by using ULE material will reduce about 70% of weight. Thermal controlling system will also be equipped for the CLST, which including Heat-Stop, primary mirror, tube truss, mount and the other optics elements. An experimental system for validating thermal controlling of primary mirror and Heat-Stop has been built, and the temperature tracking results will be illustrated in this paper. Currently, we have finished the detailed design of the CLST, and some important components also have been manufactured and finished. In this paper, we describe some important progresses and the latest status of the CLST project during these two years.
For better understanding and forecasting of solar activity, high resolution observations for the Sun are needed. Therefore, the Chinese Large Solar Telescope (CLST) with a 1.8-m aperture is being built. The CLST is a classic Gregorian configuration telescope with an open structure, alt-azimuth mount, retractable dome, and a large mechanical de-rotator. The optical system with an all reflective design has a field of view of larger than 3 arc-min. The 1.8-m primary mirror is a honeycomb sandwich fused silica lightweight mirror with an ultra lower expansion material and active cooling. The adaptive optics system will be developed to provide the capability for diffraction-limited observations at visible wavelengths. The CLST design and development phase began in 2011 and 2012, respectively. We plan for the CLST’s start of commission to be in 2017. A multiwavelength tomographic imaging system, ranging from visible to near-infrared, is considered as the first light scientific instrument. The main system configuration and the corresponding postfocal instruments are described. Furthermore, the latest progress and current status of the CLST are also reported.
In order to choose enclosure for the next generation telescopes, numerical simulation method was used. Firstly, the
telescope, two general kinds of enclosures structure and the external flow field model were established, Then
CFD(Computational Fluid Dynamics) technology was used to analyze the wind speed, static pressure, turbulence kinetic
energy distribution and eddy around the telescope, when the telescope at two different pointing gestures and the external
wind speed at 10m/s. The simulation results showed that when the telescope adapt the retractable enclosure, the wind speed
of the main optical path between 6.1 m/s and 9.3 m/s, and the average static pressure (gauge pressure) on the primary
mirror between 42.9268 Pa and 37.5579 Pa, however when telescope adapt the hemispherical enclosure, the wind speed of
the main optical path between 3.4 m/s and 6.8 m/s, the average static pressure (gauge pressure) on the primary mirror
between 12.1387 Pa and 11.105 Pa. Although the wind resistance of the retractable enclosure was lower than the
hemispherical enclosure, no eddy generated near the main optical path, it provided the telescope a uniform flow field and
ensured the quality of the image of a star. So the retractable enclosure would have better performance than the
CCD60, developed by e2v technologies, is a 128x128 pixel frame-transfer back-illuminated sensor using the
EMCCD technology. This kind of detector has some attractive characteristics, such as high frame rate, low noise and
high quantum efficiency. So, it is suitable for Adaptive Optical Wave Front Sensor (AO WFS) applications. However, the
performance of this detector is strongly depended on its temperature. In order to achieve high multiplication gain and low
dark current noise, CCD60 should be cooled under -45℃. For this reason, we had designed a cooling system to cool
down the CCD60 detector base on thermoelectric cooler. Detail of the design, thermal analysis and the cooling
experiment are presented in this paper. The performance of multiplication gain after cooling had been tested too. The
result of cooling experiment shows that the thermoelectric cooler can cool the CCD to below -60 °C under air cooled
operation and an air temperature of 20 °C. The multiplication gain test tell us the multiplication gain of CCD60 can
exceed 500 times on -60℃.
For better understanding and forecasting of the solar activity and the corresponding impacts human technologies and life on earth, the high resolution observations for Sun are needed. The Chinese Large Solar Telescope (CLST) with 1.8 m aperture is being built. The CLST is a classic Gregorian configuration telescope with open structure, alt-azimuth mount, retractable dome, and a large mechanical de-rotator. The optical system with all reflective design has the field of view of larger than 3 arc-minute. The 1.8 m primary mirror is a honeycomb sandwiches fused silica lightweight mirror with ULE material and active cooling. The adaptive optics system will be developed to provide the capability for diffraction limited observations at visible wavelengths. The CLST design and development phase began in 2011 and 2012 respectively. We plan for the CLST’s starting of commission in 2017. A multi-wavelength tomographic imaging system with seven wavelengths range from visible to near-infrared wavelength is considered as the first light scientific instruments. In this paper the main system configuration and the corresponding post focal instruments are described. Furthermore, the latest progress and current status of the CLST are also reported.
High precision pointing and tracking is an important performance indicator of the telescope, and tracking is implemented mainly by the azimuth axis and the altitude axis movement together method for alt-azimuth designed telescopes, and as a control feedback angle encoder must be installed on the azimuth axis, pitch axis. Scale tape grating encoder due to the advantages of non-contact measurement, high precision, simple assembly and adjustment, as a new generation of angle encoders has been widely used in modern telescopes’ angle measuring system. However performance of these systems can be limited by the factors of mechanical installation, machining error, random error, and other types of error, which often fail to meet arcsecond or sub-arcsecond angle measurement requirements. This paper analyzes the impacts of the mechanical installation eccentric, the roundness error, shafting sloshing on encoder angle measuring, and develops a 4 reading heads, which have 90 ° phase difference, software subdivision angle measurement program. And we make counterclockwise and clockwise angle measuring experiments on a experimental platform, which has mechanical installation eccentric 10um, roundness error 2um and shafting sloshing 0.6". Two sets of experiments measuring angle error RMS values are 0.387'' and 0.487''. The experiments prove that the program can eliminate the angular measurement error due to the mechanical installation the eccentric, machining roundness error, shafting sloshing, achieve arcsecond angle measuring.
During telescope detection, there is atmosphere overflow and other stray light affecting the system which leads to background disturbance. Thus reduce the detection capability of the system. So it is very necessary to design mechanical structure to suppress the stray light for the telescope detection system. It can both improve the signal-to-noise and contrast of the object. This paper designs the optical and mechanical structure of the 400mm telescope. And then the main baffle, baffle vane, field stop and coating technology are used to eliminate the effect of stray light on the optical and mechanical system. Finally, software is used to analyze and simulate stray light on the whole optical and mechanical system. Using PST as the evaluating standard, separate and integrated analysis of the suppressing effect of main baffle, baffle vane and field aperture is completed. And also get the results of PST before and after eliminating the stray light. Meanwhile, the results of stray light analysis can be used to guide the design of the optical and mechanical structure. The analysis results demonstrate that reasonable optical and mechanical structure and stray light suppression measure can highly reduce the PST and also improve the detection capability of the telescope system, and the designed outside baffle, inside baffle, vanes and coating technique etc. can decrease the PST approximately 1 to 3 level.
To satisfy the requirement of large telescope, a large aperture focal plane shutter with aperture size of φ200mm
was researched and designed to realize, which could be started and stopped in a relative short time with precise position,
and also the blades could open and close at the same time at any orientation. Timing-belts and stepper motors were
adopted as the drive mechanism. Velocity and position of the stepper motors were controlled by the PWM pulse
generated by DSP. Exponential curve is applied to control the velocity of the stepper motors to make the shutter start and
stop in a short time. The closing/open time of shutter is 0.2s, which meets the performance requirements of large
In the large telescope using hydrostatic bearings, what will happen if the deformation of supporting pad and sliding
surface exceed expectation? Obviously, mechanical reliability of the telescope will be bad. In order to decrease this
deformation of a large telescope, yoke of the telescope was optimized. The principle and process of this work and Finite
Element Analysis (FEA) are introduced in detail. According to the FEA result, the deformation of supporting pad
decreases 32% and sliding’s decreases 36.7% after optimizing. The result shows that this work is effective to decrease
the deformation of the two important surface and helpful to promote mechanical reliability of the telescope.
We are developing a sodium guide star adaptive optics system for the 1.8 meter telescope, which consists of three
main parts: (i) 20W microsecond pulsed laser system, (ii) Φ200mm laser launch telescope and (iii) 37-elements adaptive
optics system. All of these three parts are mounted on the 1.8 meter telescope which is located in Gaomeigu site of
Yunnan Astronomical Observatory, Chinese Academy of Sciences. The pulsed laser system and the launch telescope are
rotated with the azimuthal base of the telescope. A miniaturized 37-elements low-order adaptive optics system including
a 37-elelment deformable mirror and a 6x6 array Hartmann-Shack wavefront sensor is mounted at the Cassegrain focus
taking account of the pulsed laser mode. A separate tip-tilt correction loop is also integrated into the system. This paper
describes the details of this system, the simulation result and the test result in the lab. After the indoor test, the whole
system will be shipped to 1.8 meter telescope. The latest commissioning status and results is presented also in this paper.
In 2009, A 127-element adaptive system had been manufactured and installed at the Coude room of the 1.8-meter
telescope at the Gaomeigu site of Yunnan Astronomical Observatory, Chinese Academy of Sciences. A set of new
adaptive optical system based on a 73-element deformable secondary mirror is being developed and will be integrated
into the 1.8-meter telescope. The 73-element deformable secondary mirror with convex reflecting surface is designed to
be compatible with the Cassegrain focus of the 1.8-meter telescope. Comparing with the AO system of Coude focus, the
AO system on the deformable secondary mirror adopts much less reflections and consequently restrains the thermal
noise and increases the energy transmitting to the system. The design and simulation results of this system will be
described in this paper. Furthermore, the preliminary test result of the deformable secondary mirror in the lab is also presented.
The 127-element adaptive optical system for the 1.8m astronomical telescope is being developed. In this system, the
wavefront correction loop consists of a 127-element deformable mirror, a Hartmann-Shack (H-S) wavefront sensor, and
a high-speed digital wavefront processor. The tracking system consists of a tip-tilt mirror, a tracking sensor and a
tracking processor. The wavelength for the H-S wavefront sensor ranges from 400-700nm. The imaging observation
wavelengths range from 700-1000nm and 1000-1700nm respectively. In this paper, the optical configuration of 1.8m
telescope will be briefly introduced. The 127-element adaptive optical system is described in detailed. Furthermore, the
preliminary performances and test results on the 127-element adaptive optical system is reported.
Cryogenic optical system undergoes wide temperature change; therefore it must be athermal. That means when the system is cooled down to very low temperature, its imaging property should be kept as good as at room temperature. One way to achieve athermal optical system requires that all optical and mechanical parts in the system be made from same material. An all-reflective cryogenic optical system was thus developed in IOECAS, in which aluminum alloy was utilized to make such a system. This paper describes the key techniques for manufacturing this cryogenic optical system: material selection, forging process of the aluminum alloy blanks, initial machining, heat treatments, and final figuring. The cryogenic test of the developed system proved the validity of the manufacturing process.
An all aluminum reflective optical system was tested to evaluate its optical performances at near liquid nitrogen temperature. A special cryogenic dewar was designed and fabricated with an optical window made of quartz glass on the front wall of the dewar. The optical system under test and a reference plane mirror, which were mounted into the dewar and cooled by liquid nitrogen, formed a double pass interferometric test schema together with a He-Ne interferometer of Fizeau type outside the dewar. The test results showed that there was little differences between the wavefront errors before and after the optical system is cooled, and in both cases the optical system had a diffraction limited imaging quality.
Up to now, as large as seven times of Rayleigh-range or more is needed in measuring the far-field Gaussian beam divergency. This method is very inconvenient for the determination of the output beam divergency of the industrial product such as He-Ne lasers and the measuring unit will occupy a large space. The measurement and the measuring accuracy will be greatly influenced by the environment. Application of the Ronchi ruling to the measurement of far-field divergency of Gaussian beam in near-field is analyzed in the paper. The theoretical research and the experiments show that this measuring method is convenient in industrial application. The measuring system consists of a precision mechanical unit which scans Gaussian beam with a microdisplaced Ronchi ruling, a signal sampling system, a single-chip microcomputer data processing system and an electronic unit with microprinter output. The characteristics of the system is stable and the repeatability errors of the system are low. The spot size and far-field divergency of visible Gaussian laser beam can be measured with the system.