CATAVIÑA is a near-infrared camera system to be operated in conjunction with the existing multi-purpose nearinfrared
optical bench "CAMALEON" in OAN-SPM. Observing modes include direct imaging, spectroscopy, Fabry-
Perot interferometry and polarimetry. This contribution focuses on the optomechanics and detector controller
description of CATAVIÑA, which is planned to start operating later in 2006. The camera consists of an 8 inch LN2
dewar containing a 10 filter carousel, a radiation baffle and the detector circuit board mount. The system is based on a
Rockwell 1024x1024 HgCdTe (HAWAII-I) FPA, operating in the 1 to 2.5 micron window. The detector
controller/readout system was designed and developed at UNAM Instituto de Astronomia. It is based on five Texas
Instruments DSK digital signal processor (DSP) modules. One module generates the detector and ADC-system control,
while the remaining four are in charge of the acquisition of each of the detector's quadrants. Each DSP has a built-in
expanded memory module in order to store more than one image. The detector read-out and signal driver subsystems
are mounted onto the dewar in a "back-pack" fashion, each containing four independent pre-amplifiers, converters and
signal drivers, that communicate through fiber optics with their respective DSPs. This system has the possibility of
programming the offset input voltage and converter gain. The controller software architecture is based on a client/server
model. The client sends commands through the TCP/IP protocol and acquires the image. The server consists of a
microcomputer with an embedded Linux operating system, which runs the main program that receives the user
commands and interacts with the timing and acquisition DSPs. The observer's interface allows for several readout and
image processing modes.
A novel hydrodynamic radial polishing tool (HyDRa) is presented. It performs corrective lapping and fine polishing of diverse materials by means of a low-cost abrasive flux and a hydrodynamic suspension system that avoids contact of the tool with the working surface. With this tool it is possible to polish aspheres and free-form optics on diverse materials and sizes. The functioning principle is based on the generation of a grazing, high-velocity, low-pressure, rotational, variable density, abrasive flux with radial geometry. It has the advantage of avoiding fallen edges during the polishing process as well as reducing tool wear out and deformation. The polishing process is repeatable and achieves high degrees of precision and accuracy on optical and semiconductor surfaces. This tool is particularly useful for polishing thin substrates such as membranes and semiconductors since it can be biased for a non-interactive action on the work piece. An additional advantage of this new tool is the possibility to perform in-process interferometric measurements. Polishing results on assorted materials using HyDRa are presented.
New results using hydrodynamic radial polishing techniques on assorted materials, using HyDRa are presented. This tool performs corrective lapping and fine polishing by means of a low-cost, foamy abrasive flux. The functioning principle is based on the generation of a grazing, high-velocity, low-pressure, rotational, variable density, abrasive flux with radial geometry. It is currently possible to polish aspheres and free-form optics on diverse materials and sizes. This tool is particularly useful for polishing thin substrates such as membranes and semiconductors since it can be biased for a non-interactive action on the work piece. This process also has the advantage of achieving high removal rates. In order to achieve high degrees of accuracy and repeatability in the HyDRa finishing process, fully automated bias and slurry supply units must be incorporated to the polishing system. The air and slurry supply systems are described, as well as operational tool parameters for optimal polishing performance.
A novel hydrodynamic radial polishing tool (HyDRa) is presented. It performs corrective lapping and fine polishing of diverse materials by means of a low-cost abrasive flux and a hydrostatic suspension system that avoids contact of the tool with the working surface. With this tool it is currently possible to polish aspheres and free-form optics of up to 2.5 meters in diameter. It has the advantage of avoiding fallen edges during the polishing process as well as reducing tool wear out and deformation. The functioning principle is based on the generation of a high-velocity, high-pressure abrasive emulsion flux with radial geometry. The polishing process is repeatable and achieves high degrees of precision and accuracy on optical and semiconductor surfaces. An additional advantage of this new tool is the possibility to perform in-process interferometric measurements. Recent results of polished aspheres are discussed.
We present a new algorithm that applies the correlation functions to phase shifting interferometry to recover the phase of a test surface. In this work we make numerical simulations to test the algorithm and the results are verified with real interferograms. The correlation algorithm recovers the phase value with 5% accuracy.
In order to overcome classic polishing techniques, a novel hydrodynamic radial polishing tool (HyDRa) is presented; it is useful for the corrective lapping and fine polishing of diverse materials by means of a low-cost abrasive flux and a hydrostatic suspension system that avoids contact of the tool with the working surface. This tool enables the work on flat or curved surfaces of currently up to two and a half meters in diameter. It has the advantage of avoiding fallen edges during the polishing process as well as reducing tool wear out and deformation. The functioning principle is based on the generation of a high-velocity, high-pressure, abrasive emulsion flux with radial geometry. The polishing process is repeatable by means of the control of the tool operational parameters, achieving high degrees of precision and accuracy on optical and semiconductor surfaces, with removal rates of up to 9 mm3/hour and promising excellent surface polishing qualities. An additional advantage of this new tool is the possibility to perform interferometric measurements during the polishing process without the need of dismounting the working surface. A series of advantages of this method, numerical simulations and experimental results are described.
HyDRa is a hydrodynamic radial polishing tool ideal for the corrective lapping and fine polishing of diverse materials by means of an accelerated abrasive flux. The roughness of an optical surface is analysed for a continuous manufacturing process, beginning with the basic generation steps up to a finished optical surface. These results were obtained using a Linnik interferometer.
The wavefront sensor is an important part of active control for an Active Optics System (AOS). The wavefront sensibility of a beam compressor is experimentally tested on the 2.1m telescope at SPM. This is a simple wavefront sensor based on the wave propagation equation. A qualitative analysis of the experimental data is presented. It is concluded that the beam compressor has enough sensibility to be used as a wavefront sensor for the AOS.
Two main trends presently prevail in ELT design: arrays of hundreds of small (1 - 2 m) hexagonal mirrors and the use of several large (~8m) monolithic mirrors. We present a conceptual study of an off axis 8 m telescope with different mirror options, which can be useful as an experiment towards the design of large multi-mirror telescopes, in terms of different mirror materials, ideas for the optics and new solutions for the telescope mechanical assembly.
We present the dual IR camera CID for the 2.12 m telescope of the
Observatorio Astronomico Nacional de Mexico, IA-UNAM. The system
consists of two separate cameras/spectrographs that operate in
different regions of the IR spectrum. In the near IR, CID comprises a direct imaging camera with wide band filters, a CVF, and a low resolution spectrograph employing an InSb 256 x 256 detector. In the mid IR, CID uses a BIB 128 x 128 detector for direct imaging in 10 and 20 microns. Optics and mechanics of CID were developed at IR-Labs
(Tucson). The electronics was developed by R. Leach (S. Diego). General design, construction of auxiliary optics (oscillating
secondary mirror), necessary modifications and optimization of
the electronics, and acquisition software were carried out at OAN/
UNAM. The compact design of the instruments allow them to share
a single dewar and the cryogenics system.
We propose a method for piston errors detection in a segmented surface by means of the classical ronchi test. This consists in comparing the ronchigram fringes frequency of a reference and piston segment. The comparison is developed for the correlation method of the intensity vs pixels curves of the reference and piston segment. The presence of the piston term in a ronchigram is assured experimentally for the shack interferometer, it is by observing the coincidence rings centered type fizeau in each segment. The proposed method is applied to a segmented spherical surface with a two segment mirrors, and resolutions of piston ⩾63 ηm are experimentally obtained.
We report experimental results and analysis about a new hydrodynamic radial tool (HyDra, patent pending), which expels a suspension of water and polishing particles radially on glass. With this method it is possible to locally shape optical surfaces. The depth of material removed by HyDra grows linearly with the time. The removal rate is independent of the velocity between the tool and the glass element. The HyDra has been used to fabricate successfully an optical flat and Schmidt surface.
It has been known that in BIB type, Si:As Mid-IR detectors the internal gain can be strongly related to the internal noise. We prove that by modifying the internal gain it is possible to increase the signal-to-noise ratio to a level which is consistent with poissonian statistics only.
We propose one method for the phase alignment of segmented mirrors with piston errors. For this, we use the classical Ronchi test to observe fringes around of curvature center, after we take some lines on the Ronchi image for each segment mirror and obtain its intensity vs. pixels, to do the correlation and approximate the amount of pixels or piston displacement for the phase misalignment. Additionally, we get parabolic fit to find resolutions of sub-pixels. At the same time, we use the Shack Interferometer to observe behavior rings centered for this two segment mirrors to compare with the fringes produced with Ronchi test and to achieve resolutions of piston >= 24 (eta) m.
We present an active, low cost hydrostatic shoe bearing system for the Mexican Infrared Telescope which solves the suspension and motion of a 100 ton, 7.8 m telescope. Different geometries are analyzed to optimize the shoe's pressure print. These designs offer a self-adjusting action between the shoe's sliding path and the girth track. Different parameters such as pressure, temperature and proximity are measured and implemented into a control system in order to stabilize the bearing from the fluid's thermal viscosity effects. A simple method for fluid injection is discussed.
We present the conceptual design of the primary mirror support system of the 7.8 m Mexican Infrared-Optical Telescope. The primary mirror consists of 19 hexagonal off- axis parabolic Zerodur segments, which are carried by a tubular, lightweight and high stiffness cell structure. Each segment is actively supported by 19 pneumatic actuators, that cover the whole back area and provide a uniform force distribution. The array of actuators will be able to correct for high order aberrations. Each of these actuators contains a hydraulic damping system to provide a stiff coupling to the tubular cell to sustain the wind buffeting. The tip/tilt and piston control of each segment will be done through three axial, nanometer resolution position defining actuators. The lateral positioning of each segment is performed through 3 independent electro-mechanical actuators. With the combination of the whole set of actuators and differential positioning sensors, the phasing or coherent superposition of images of the segments, will be more feasible. The whole system will be cost effective, since several subsystems have already been tested on our 2.1 m telescope.
Optical testing of the 2.1-m telescope in San Pedro Martir, Observatorio Astronomico Nacional de Mexico, by the methods of wavefront curvature sensing and bi-Ronchi analysis, has shown that the telescope suffered of large amounts of astigmatism. We identified these as due to improper primary mirror support and developed an active control system to correct for it. The number and position of the actuators were decided in accordance to the flexural modes that needed to be corrected, resulting in a system of 18 pressure controlled pneumatic actuators, with an outer loop that verifies the load at three hard points. A PID algorithm and matrix inversion are fundamental parts of this outer loop, that guarantees that the M1 mirror is tilted as a rigid body to maintain it properly aligned. The successful performance of the system to correct low order aberrations is reported.
We present the Mexican Infrared-Optical New Technology Telescope Project (TIM). The design and construction of a 7.8 m telescope, which will operate at the Observatorio Astronomico Nacional in San Pedro Martir, B.C. (Mexico), are described. The site has been selected based on seeing and sky condition measurements taken for several years. The f/1.5 primary mirror consists of 19 hexagonal off-axis parabolic Zerodur segments. The telescope structure will be alt-az, lightweight, low cost, and high stiffness. It will be supported by hydrostatic bearings. The single secondary will complement a Ritchey-Chretien f/15 design, delivering to Cassegrain focus instrumentation. The telescope will be infrared optimized to allow observations ranging from 0.3 to 20 microns. The TIM mirror cell provides an independent and full active support system for each segment, in order to achieve both, phasing capability and very high quality imaging (0.25 arcsec).
We are developing an instrument to study the morphology and kinematics of the molecular gas and its interrelationship with the ionized gas in star forming regions, planetary nebulae and supernova remnants in our Galaxy and other galaxies, as well as the kinematics of the IR emitting gas in starburst and interacting galaxies. This instrument consists of a water-free fused silica scanning Fabry-Perot interferometer optimized in the spectral range from 1.5 to 2.4 micrometers with high spectral resolution. It will be installed in the collimated beam of a nearly 2:1 focal reducer, designed for the Cassegrain focus of the 2.1 m telescope of the San Pedro Martir National Astronomical Observatory. Mexico, in its f/7.5 configuration, yielding a field of view of 11.6 arc-min. It will provide direct images as well as interferograms to be focused on a 1024 X 1024 HAWAII array, covering a spectral range from 0.9 to 2.5 micrometers .
The design concepts of a mid-IR camera/spectrograph, based on a HUGHES/SBRC 320 by 240 Si:As IBC sensor chip assembly (SCA), are presented, The system will operate in the 2 to 28 micrometers wavelength interval and will be optimized in the 10 micrometers regime. This SCA is divided into 32 regions, each with an independent output. The outputs, after being amplified and sampled, are multiplexed into 8 high speed 16 bit A/D converters. The initial configuration allows readout rates of up to 60 frame/s. A higher speed frame readout configuration is foreseen. A 32 bit deep memory and a high speed ALU, synchronized to the detector, will co- add/subtract the frames, making a real time visualization during the integration process possible. The detector, reflective optics, low resolution gratings, several cold stops, baffles, up to 12 filters and a CVF will be allocated in a 10 inch diameter working surface LN2/LHe dewar. The system will be linked to a workstation, providing a user friendly environment. The system is planned to operate at the Observatorio Astronomic Nacional in San Pedro Martir, B.C., Mexico.
We describe the configuration and operation modes of the IR camera/spectrograph: TEQUILA based on a 1024 X 1024 HgCdTe FPA. The optical system will allow three possible modes of operation: direct imaging, low and medium resolution spectroscopy and polarimetry. The basic system is being designed to consist of the following: 1) A LN2 dewar that allocates the FPA together with the preamplifiers and a 24 filter position cylinder. 2) Control and readout electronics based on DSP modules linked to a workstation through fiber optics. 3) An opto-mechanical assembly cooled to -30 degrees that provides an efficient operation of the instrument in its various modes. 4) A control module for the moving parts of the instrument. The opto-mechanical assembly will have the necessary provision to install a scanning Fabry-Perot interferometer and an adaptive optics correction system. The final image acquisition and control of the whole instrument is carried out in a workstation to provide the observer with a friendly environment. The system will operate at the 2.1 m telescope at the Observatorio Astronomico Nacional in San Pedro Martir, B.C. (Mexico), and is intended to be a first-light instrument for the new 7.8m Mexican IR-Optical Telescope.