Patent ID: 6404547
Filing Date: 2002-06-11
Classification: G02B

Abstract:
A centrally-obscured reflective telescope comprising:a telescope housing having an input window; an inner housing; a primary mirror attached to a first end of the inner housing; a secondary mirror attached to a second end of the inner housing by a plurality of support struts that suspend the secondary mirror between the input window and the primary mirror; and a semi-active focus and thermal compensation system comprising: a heating element disposed on each of the support struts; a first temperature sensor that generates a reference temperature; a second temperature sensor disposed on the secondary mirror; a temperature sensor disposed on each of the support struts; and a temperature compensation controller coupled to each heating element and to the temperature sensors that senses the reference temperature and the temperatures of the support struts and secondary mirror and controls the heat output of each heating element to selectively heat the support struts to control the position of the secondary mirror relative to the primary mirror.