Patent ID: 6181881
Filing Date: 2001-01-30
Classification: G03B

Abstract:
A field-of-view frame switching device comprising:a rectangular fixed field-of-view frame of a predetermined size;a mask for providing an actual field-of-view frame having a variable size, wherein the actual field-of-view frame establishes an actual field-of-view frame size being used in the field-of-view frame switching device, the mask being composed of:a plurality of light-shielding members for covering portions of said rectangular fixed field-of-view frame so as to vary the actual field-of-view frame size, said light-shielding members comprising a first pair of oppositely arranged light-shielding members and a second pair of oppositely arranged light-shielding members; anda plurality of coupling members for coupling the first pair of light-shielding members to the second pair of light-shielding members, whereinsaid first and second pairs of light-shield members are all moved simultaneously, andwhen said first pair of light-shielding members are positioned closer to each other to narrow the actual field-of-view frame, said second pair of light-shielding members are positioned wider apart from each other than a second pair original set position at which said second pair of light-shielding members do not narrow the actual field-of-view simultaneously with the positioning of the first pair of light-shield member, and when said first pair of light-shielding members are positioned wider apart from each other than a first pair original set position at which said first pair of light-shielding members do not narrow the actual field-of-view, said second pair of light-shielding members are positioned closer to each other to narrow the actual field-of-view frame simultaneously with the positioning of the first pair of light-shield member; anda moving member for moving at least one lighting-shielding member of said plurality of light-shielding members in a direction substantially parallel to one side of said rectangular fixed field-of-view frame.