Optical: systems and elements – Mirror – Including specified control or retention of the shape of a...
Patent
1992-09-24
1995-07-04
Shafer, Ricky D.
Optical: systems and elements
Mirror
Including specified control or retention of the shape of a...
359849, 359851, 359853, 359859, 359861, 359868, 359869, G02B 510
Patent
active
054305772
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a double reflector of the type having two spaced
apart primary mirrors oriented toward a common focal point.
Such a double reflector is known from DE-OS 19 40 657. With this known double reflector the primary mirrors as well as the secondary deflector mirror are of monolithic rotationally symmetrical design and that is disadvantageous for the reason that the system poses limitations on the diameter of such mirrors. Another disadvantage is the provision of a single rotationally symmetrical secondary deflector mirror because it reduces the effective light intensity due to the common focussing. Moreover, the secondary deflector mirror is not integrated in the real time measuring and compensating system and that has an unfavorable effect on the image quality to be achieved.
A central-axis reflector comprising a primary mirror whose diameter is 20 m is known from the publication SPIE, vol. 1013 "Optical Design Methods, Applications, and Large Optics" (1988), pages 241-248. This very big primary mirror which can be used also as an off-axis reflector is realized by a plurality of individual segments which are placed in contiguous relationship.
A large telescope including a primary mirror which is deformable with the aid of actuators for correction of the wavefront, with corresponding adaptive compensation measures taking place in real time, is known from the publication Phys. Bl.44 (1988), no. 12, pages 439-446.
It is the object of the invention to improve a double reflector of the kind mentioned initially in respect of the effective light intensity and image quality.
The above and other objects and advantages of the present invention are achieved by the novel features of the present invention as described in detail below.
The invention provides a gain in light intensity by the arrangement of a separate secondary mirror segment which is coordinated with each primary mirror segment and adapted in shape to the respective primary mirror segment. Improved image quality is achieved, according to the invention, in that also the secondary mirror segments are included in the real time measuring and compensating system so that both the primary mirror segments and the secondary mirror segments are separately adjustable.
According to an advantageous further development of the invention the inherent mass of the individual mirrors is reduced by the fact that the mirrors comprise a support structure formed with cavities. A reduced inherent mirror mass furthermore has a favorable effect on the adjustability of the mirrors and thus also on the image quality which is achievable with the double reflector. In this respect it is also advantageous that the mirrors are specifically cooled by a coolant which circulates in the cavities. Another advantage for the image quality to be achieved is the further development of the invention according to which all the mirrors and all the operating and auxiliary means are arranged on a common self-supporting support member which is supported hydrostatically, over a large area, in a tray so as to be rotatable about its axis of elevation and the common optical axis.
The invention will be described in greater detail below with reference to an embodiment illustrated in the drawing. Here the double reflector is used as a mirror telescope.
FIG. 1 diagrammatically shows a vertical cross section of a mirror support system of a mirror telescope comprising two off-axis hyperbolical reflectors;
FIG. 2 diagrammatically shows a top plan view of the mirror support system according to FIG. 1;
FIGS. 3 and 4 each show diagrammatically a cross section of the mirrors and the mirror support system according to FIGS. 1 and 2 with different mirror arrangements;
FIGS. 5 and 6 each diagrammatically show details of the mirror arrangement according to FIG. 4;
FIG. 7 shows a perspective illustration, partly in section, of the reflector support system according to FIGS. 1 and 2, as is applied also with other reflector surface curvatures;
FIG. 8 diagrammatically shows an overall view of a mirror te
REFERENCES:
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patent: 5136413 (1992-08-01), MacDonald et al.
patent: 5347401 (1994-09-01), Hugenell
Optical Design Methods, Applications, and Large Optics; Andre Masson et al; SPIE vol. 1013 (1988) pp. 240-248.
Aktive und adaptive Optik in der Astronomie; Von F. Merkle; Physik-Verlag GmbH, 1988; pp. 439-446.
Advanced Technology Optical Telescopes IV; Lawrence D. Barr; SPIE vol. 1236 1990; pp. 85-90.
Angstenberger Karl F.
Hugenell Hermann
Shafer Ricky D.
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