3-MIRROR APLANATIC TELESCOPE WITH LOW DIFFRACTION SIDELOBES

A three-mirror rotationally symmetric telescope has been designed in w hich the secondary and tertiary mirrors are behind the primary. In thi s configuration the mounting structure of the secondaries need not int errupt the light path, thus avoiding the production of undersirable di ffraction sidelobes. In a 1-degrees total field of view the image blur circle is less than 3 arcmin. The design has application in the milli meter and submillimeter wavelength regions for problems in which low r esponse to far-off-axis sources is critical.