Peumans, the optical advantages of curved focal plane. An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. Best telescope for astrophotography 2020 types, price range. In astronomy, wide survey telescopes require a novel camera design. Barlow a barlow lens is a lens that multiplies the focal length of the optical system, giving more magnification and increasing focal length, but at a slower system speed. Cooling the darpa space surveillance telescope sst. The focal length is the distance from the lens or mirror center to where the collected light is focused. A 15 wide field of view imaging air cherenkov telescope. Wide fieldofview curved focal plane array semantic scholar. Smaller, lighter 8200mm f2 roweackermann schmidt astrograph rasa ideal for mediumsized mounts flat field free of optical aberrations like field curvature, coma, astigmatism and chromatic aberration across an entire apsc sensor. Innovative focal plane design for high resolution imaging and earth observation. Telescope fp more compact reduce the mass find optical solutions long focal plane long telescope length pushbroom imager swath. M1 crab nebula m2 m3 m4 m5 m6 butterfly cluster m7 the scorpions tail m8 lagoon nebula m9 m10 m11 wild duck cluster m12 m hercules globular cluster m14 m15 m16 associated with the eagle nebula m17 omega.
Combining freeform optics and curved detectors for wide. It can capture stunning deepsky astronomical images without the challenges typically presented by longer focal length instruments. The 8 rasa is an imaging telescope that delivers a flat field without optical aberrations for razor sharp stars across a wide field of view. Curved sensor, optical design, petzval field curvature. It is so named because it is usually the lens that is closest to the eye when someone looks through the device.
The optical designs have been done by the software zemax. Combining freeform optics and curved detectors for wide field. These youtube videos link1, link2 provide more information on how the sst operates. Peumans, the optical advantages of curved focal plane arrays. Developed at mit lincoln lab, the sst features the first implementation of recent advances in curved focal plane technology enabling a wide field of view, rapidly scanable, and threemirror, 3.
This design choice produces a much larger fov than the fov of a. Today however, with computer aided optimization, high image quality can be achieved over flat focal surfaces. Mait, spacebandwidth scaling for wide fieldofview imaging. Wide angle eyepiece celestron telescopes, telescope. The last decade has seen significant interest in wide field of view fov telescopes for sky survey and space surveillance applications. Most telescopes will have a curved focal plane and comatic aberration, particularly short focal length refractors. The entrance pupil the stop is located at the schmidt corrector. Shaw montana state university conics a conic is a surface of revolution formed by spinning a conic section around the axis. Plus each axiom eyepiece is optimized to deliver pinpoint images when used with a flat field telescope. Along with the newly designed optics, the edgehd also has a redesigned optical tube guaranteed to help you get the maximum performance from your instrument. For some telescope designs, the image plane is significantly curved, so that sharp images could not be obtained over the whole image area when using a flat image sensor.
Telescope fundamentals dunlap institute university of toronto. Pdf a fast, widefield and distortionfree telescope. Each of the primary, secondary, tertiary, and quaternary reflective surfaces are rotationally symmetric about the optical axis. However, miniaturization could be achieved, without decreasing resolution and sensibility, by. Specifically, schmidttype systems provide by far the largest number of focal plane spatially resolved pixels on the focal plane per optical element.
After the light enters through the aperture, it travels a certain distance to the focal plane. Curved focal plane detector array for wide field cameras. The schmidt telescope achieves wide field of view with spherical mirrors, but it is difficult to scale up because of. The schmidt telescope has a curved focal plane, which is con focal with the mirror. A fast, widefield and distortionfree telescope with curved. An offaxis, widefield, diffractionlimited, reflective. Optomechanical design and manufacturing issues are also discussed. Optical system design s15 reflector telescopes joseph a. Most sky survey work is still accomplished by smaller projects with significantly less funding. For imaging applications, curved focal planes are not an obvious choice. Celestron celestron cgem ii 1100 hd camera concepts.
A hemispherical electronic eye camera based on compressible. Best telescope for astrophotography 2020 types, price. This plane is therefore accessible as a location for a graticule or micrometer crosswires. Modern design techniques incorporating reflective and refractive correctors appear to make a curved focal surface an unnecessary complication. They provide a possibility to build fast, wideangle and highresolution systems, which are very compact and free of obscuration. Osa combining freeform optics and curved detectors for. The wide field of view helps you bring subjects into the field of view quickly. Aizi 1 where cx and cy are the curvature of the surface along the x and y. Aperture, focal length, and focal ratio are all corelated. Are curved focal planes necessary for widefield survey. Moreover, it is possible to work at very fast fratios, below f1, thereby minimizing the obscuration and weight of the camera, and the.
Curved focal plane wide field of view telescope design. Innovative focal plane design for large space telescope using. Examination of seven current, wide fov projects sdss, mmt, dct, lsst, panstarrs, hypersuprime and darpa sst suggests there is little to be gained from a curved focal plane. Curved sensor, optical design, petzval field curvature, high resolution. The focal plane array was then transfer printed from the hemispherical transfer element onto a matching concave glass substrate coated with a thin layer of photocurable adhesive noa 73, norland. Scta combination of the schmidt and cassegrain design concepts yielding a moderately wide field of view and easy access to the focal plane. The larger viewing area also makes it easier to follow subjects as they move. Learn more about the benefits and features of this.
Function mtf was calculated in zemax lens design software for different. Of all telescope designs, the schmidt telescope, and solutions derived from it, provides the widest fov. This is essentially the richest field telescope design as championed by mel bartels. Curved sensors for compact highresolution wide field designs. However, the field of freeform surfaces design techniques still remains underexplored. The spherical aberration is corrected with an aspheric corrector placed at the stop. The traditional design of optical systems is severely complicated by the curved shape of the image surface which has to be recorded on a planar retina. New ultrastable focus system six precision sealed ball. Finder a finder is a small telescope or aiming device with a wide field of view that is used to aim the main telescope to help find celestial objects. Current status of the hobbyeberly telescope wide field.
Mel based his inch f3 on a paracorr, a 6mm exit pupil and it is f3. Eric pearce professor university of arizona steward. Videorate imaging of the brains of awake mice with a field of view of 10. Videorate imaging of biological dynamics at centimetre.
Designed with colour astronomical cmos cameras, smaller ccd cameras, and mirrorless cameras in mind. Videorate imaging of biological dynamics at centimetre scale. The key enabling technology for sst is the wide fieldofview curved focal plane array wfc, a chargecoupled device ccd that corrects for the inherent aberrations of mirrors and lenses. Combining freeform optics and curved detectors for wide field imaging. Dong, easyaligned offaxis threemirror system with wide field of view using freeform surface based on integration of primary and tertiary mirror, appl. It is important to understand the optical design trade space and how cost, performance, and physical characteristics are.
The second design is a threemirror anastigmat telescope with focal length of 250 mm, fratio of 2. In order to accept light without vignetting from directions that are relatively far away from the optical axis, the mirror must be somewhat larger than the schmidt corrector. Optical design effective area, and field of view requirements of the starx telescope drive available design options 1. Pdf curved focal plane detector array for wide field cameras. The fixed magnification wide angle eyepiece is a terrific addition to your celestron spotting scope. Osa combining freeform optics and curved detectors for wide. Freeform optics for innovative focal plane design of large. Therefore, curved image sensors are used with some telescopes, where the field curvature cannot be reduced. Curved monolithic focal plane array for widesurvey. This is because magnification is equal to the telescope focal length divided by the eyepiece lens focal length. The literature to date has shown that reimaging forms have been restricted to a moderate fieldofview telescope achieves a wide field of view using spherical symmetry. Innovative focal plane design for large space telescopes. We present an offaxis f8 reflective schmidt design for the proposed kdust chinese infrared telescope at dome a on the antarctic plateau, which offers.
Develop, fabricate, and integrate a mosaic of curved focal plane arrays into a wide fieldof view detector system. And the third technology with an interest for sensors curvature was the schmidt telescope which provide wide field of view, limited aberrations with a curved detector 4. While all designs result from optimization of competing constraints, one of the more controversial design choices is whether such telescopes require flat or curved focal planes. A design concept is presented for the south pole telescope which comprises a 10 meter diameter offaxis paraboloidal primary mirror, a gregorian secondary mirror. In some eyepiece types, such as ramsden eyepieces described in more detail below, the eyepiece behaves as a magnifier, and its focal plane is located outside of the eyepiece in front of the field lens. Prompted by this interest, a multitude of widefield designs have emerged. Mtf was calculated in zemax lens design software for different fields. Jan 15, 2008 a wide field of view telescope having two concave and two convex reflective surfaces, each with an aspheric surface contour, has a flat focal plane array. This allows the two mirror surfaces to be machined on the same substrate. You may be able to get by for visual use without one, but if you intend to use this scope for photography, then expect to shell out another 150 usd for the flattener. Meeting the optical requirements of large focalplane arrays. Introduction of all the conventional astronomical telescope designs used in amateur astronomy the cassegrain is the least likely to be considered a candidate for wide field imaging applications. While the telescope has been very successful observing large samples of objects such as quasistellar objects qsos spread over the sky with surface densities of around one per 10 sq.
Jul 02, 2010 the traditional design of optical systems is severely complicated by the curved shape of the image surface which has to be recorded on a planar retina. The astrograph features a well corrected and uniformly illuminated focal plane. These requirements dictate the telescope focal length to be 5. Thirty years ago with mostly analytic design tools, the solution to widefield image quality appeared to be curved focal planes. Jin, design of a low fnumber freeform offaxis threemirror system with. The focal ratio is the ratio between the aperture and focal length. Jun 14, 2006 all recently built systems use a flat focal plane and most systems in design have either rejected curved focal planes large synoptic survey telescope lsst 9, discovery channel telescope dct 1012, or they are presently carrying the curved focal surface while attempting to design it out of their system hypersuprime camera. They provide a possibility to build fast, wide angle and highresolution systems, which are very compact and free of obscuration. The objective lens or mirror collects light and brings it to focus creating an image. With astronomical optics, long telescope focal length is associated with high magnification. Pdf curved sensors for compact highresolution wide field designs. Freeform optics and curved sensors the need of high performance in terms of image quality, high resolution and wide field of view increases the complexity and the volumemass budget of imaging systems.
Develop, test, and validate software for autonomous telescope. The spherical primary mir ror is concentric about the stop. In the recent years a significant progress was achieved in the field of design and fabrication of optical systems based on freeform optical surfaces. Simulating the optical performance of a smallsized. The edgehd 11 optics produce a focal plane threetimes flatter than the standard equivalent sct telescope with diffraction limited stars to the very edge of the nikon 300 or canon 40d sensor. A wide field of view telescope having two concave and two convex reflective surfaces, each with an aspheric surface contour, has a flat focal plane array. For example, suppose you have an 8 schmidtcassegrain telescope with a 2000mm focal length, and a 20mm eyepiece with a 50 apparent field.
The result is a very wide field of view, but with a curved focal plane. The up to a point is because there is a physical limit to the size of the apparent field of view that an eyepiece can have and that is set be the internal diameter. For all these discoveries, the use of curved sensors was possible but limited. Wide fieldofview threemirror telescope designed for.