1. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the zoom optical sytem comprises an optical-element group that is disposed on a imagemost side, the variable optical-property optical element being arranged in the optical-element group that is disposed on the imagemost side.
2. A zoom optical system according to claim 1, wherein the variable optical-property optical element has a rotationally asymmetric curved surface that has a function for compensating for decentered aberrations.
3. A zoom optical system according to claim 1, wherein the following condition is satisfied:
70\xb0\u2266\u03a6\u2266110\xb0
where \u03a6 is an angle of turning of an optical axis caused by the variable optical-property optical element.
4. A zoom optical system according to claim 1, wherein the variable optical-property optical element is driven by one of an electrostatic force, an electromagnetic force, a piezoelectric effect, and fluid.
5. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following conditions are satisfied:
0.5<EXWfW<50.0
0.5<EXTfT<50.0
where EXW is a physical distance from an exit pupil position of an optical system as viewed from the variable optical-property optical element to the variable optical-property optical element at a wide-angle end, EXT is a physical distance from an exit pupil position of the optical system as viewed from the variable optical-property optical element to the variable optical-property optical element at a telephoto end, fW is a focal length of the entire optical system at the wide-angle end, and fT is a focal length of the entire optical system at the telephoto end.
6. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following condition is satisfied:
0.3<\u03bew<0.9
where \u03bew is a magnification of a group of optical elements arranged between the variable optical-property optical element and an image surface.
7. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following condition is satisfied:
\u22125.0<(fafb)\xd7fW<\u22120.5
where fa is a focal length, at a wide-angle end, of a group of optical elements arranged on an object side of an aperture stop, fb is a focal length, at the wide-angle end, of a group of optical elements arranged on an image side of the aperture stop, and fW is a focal length of the entire system at the wide-angle end.
8. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following condition is satisfied:
D<20.0 mm
where D is an effective diameter of the variable optical-property optical element.
9. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups,
wherein the zoom optical sytem comprises, in order from an object side:
a first optical-element group having a negative optical power;
a second optical-element group having a positive optical power,
a third optical-element group having a positive optical power; and
a fourth optical-element group having a positive optical power, and
wherein the two optical-element groups movable in the magnification change are the second optical-element group and the third optical-element group.
10. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups,
wherein the zoom optical sytem comprises, in order from an object side:
a first optical-element group having a negative optical power;
a second optical-element group having a positive optical power; and
a third optical-element group having a positive optical power, and
wherein at least the second optical-element group has the magnification varying function.
11. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups,
wherein the zoom optical system comprises, in order from an object side:
a first optical-element group having a negative optical power;
a second optical-element group having a positive optical power;
a third optical-element group having a positive optical power; and
a fourth optical-element group having a positive optical power, and
wherein at least the second optical-element group has the magnification varying function.
12. An imaging apparatus comprising a zoom optical system,
the zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the zoom optical system comprises an optical-element group that is disposed on a imagemost side, the variable optical-property optical element being arranged in the optical-element group that is disposed on the imagemost side.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method for synchronizing spanning tree information between layer two (L2) devices associated with a plurality of L2 networks coupled to an intermediate network that includes a plurality of provider edge routing devices, the method comprising:
receiving information associated with a loop detection protocol from a first one of the L2 devices associated with a first one of the L2 networks, wherein the information is received as one or more bridge protocol data units (BPDUs) containing spanning tree information associated with the loop detection protocol; and
communicating a routing protocol message that includes the BPDUs through an intermediate network via a provider edge routing device in accordance with a routing protocol, wherein the routing protocol message includes the BPDUs as opaque data of the routing protocol message such that at least one routing device within the intermediate network ignores the opaque data when forwarding the routing protocol message,
wherein communicating the routing protocol message comprises communicating the BPDUs such that a second L2 device associated with a second one of the L2 networks receiving the BPDUs can maintain spanning tree information that represents the plurality of L2 networks as a single comprehensive spanning tree in which the plurality of provider edge routing devices are represented as a single node,
wherein the intermediate network does not run the loop detection protocol between the provider edge routers of the intermediate network.
2. The method of claim 1, further comprising:
executing a virtual private LAN service (VPLS) to form a virtual network between the first L2 network and the second L2 network coupled by the intermediate network; and
updating L2 topology data based on the information to reflect a topology of the first L2 network, the second L2 network, and the virtual network.
3. The method of claim 2, further comprising:
analyzing the L2 topology data with the routing device to detect any loops; and
updating a status of one or more ports of the routing device upon detecting one or more loops.
4. The method of claim 1, further comprising:
receiving BPDUs containing spanning tree information associated with the loop detection protocol from a plurality of the L2 devices; and
selecting one of the plurality of L2 devices as a root L2 device, and
wherein communicating the routing protocol message comprises communicating a routing protocol message that identifies the selected one of the plurality of L2 devices as the root L2 device.
5. The method of claim 1, wherein communicating comprises:
comparing the information associated with the loop detection protocol with topology data to determine whether a change to a topology of an L2 network has occurred; and
selectively communicating the information associated with the loop detection protocol via the routing protocol based on the comparison.
6. The method of claim 1, wherein communicating comprises communicating the a routing protocol message via the routing protocol that includes advertised routes in the routing protocol message.
7. The method of claim 1, wherein communicating comprises communicating the BPDUs via the routing protocol as network layer reachability information (NLRI) of the routing protocol message that is associated with an advertised route.
8. The method of claim 1, wherein communicating through an intermediate network comprises communicating the routing protocol message via the Border Gateway Protocol (BGP).
9. The method of claim 1, wherein receiving comprises receiving bridge protocol data units (BPDUs) containing spanning tree information in accordance with the spanning tree protocol (STP).
10. The method of claim 1,
wherein the L2 devices comprise Ethernet bridges, and
wherein the provider edge routing device comprises provider edge router.
11. The method of claim 10,
wherein receiving the information comprises:
receiving, from a plurality of Ethernet bridges, BPDUs containing spanning tree information; and
wherein communicating comprises:
selecting a subset of the information contained within the BPDUs, and
communicating the selected subset of information via the routing protocol to present the plurality of Ethernet bridges as a single Ethernet bridge.
12. A method for synchronizing spanning tree information between layer two (L2) devices associated with a plurality of L2 networks coupled to an intermediate network that includes a plurality of provider edge routing devices, comprising:
receiving, with a provider edge routing device, information associated with a layer two (L2) network loop detection protocol via a routing protocol message that includes the information as opaque data of the routing protocol message such that at least one routing device within the intermediate network ignores the opaque data when forwarding the routing protocol message,
wherein the provider edge routing device does not run the loop detection protocol between other provider edge routers of the intermediate network; and
forwarding the information as one or more bridge protocol data units (BPDUs) containing the information associated with the loop detection protocol to an L2 device associated with an L2 network such that the L2 device can maintain spanning tree information that represents the plurality of L2 networks as a single comprehensive spanning tree in which the plurality of provider edge routing devices are represented as a single node.
13. The method of claim 12, further comprising:
updating topology data in accordance with the received information; and
analyzing the topology data to determine whether any loops exist within the L2 network.
14. The method of claim 12,
wherein the information conforms to the spanning tree protocol (STP), and
wherein forwarding the information comprises forwarding the information to the L2 device in accordance with the STP.
15. The method of claim 14, wherein forwarding the information comprises:
generating bridge protocol data units (BPDUs) containing the spanning tree information; and
sending the BPDUs to the L2 device.
16. The method of claim 12, wherein receiving the information comprises receiving the information in a routing protocol message that includes advertised routes.
17. The method of claim 12, wherein receiving the information comprises receiving the information as network layer reachability information (NLRI) of the routing protocol message associated with an advertised route.
18. The method of claim 12, wherein receiving the information via a routing protocol comprises receiving the information via a routing protocol message that conforms to the Border Gateway Protocol (BGP).
19. The method of claim 12, wherein the L2 network is a first L2 network, the method further comprising:
executing a virtual private LAN service (VPLS) to form a virtual network between the plurality of L2 networks; and
updating topology data to reflect a topology of the virtual network and the plurality of L2 networks.
20. The method of claim 19, further comprising:
analyzing the topology data to detect any loops; and
updating a status of one or more ports of the provider edge routing device upon detecting one or more loops.
21. A provider edge routing device comprising:
a physical interface that receives layer two (L2) loop detection information associated with a loop detection protocol from a first one of a plurality of L2 devices associated with a first one of a plurality of L2 networks coupled to an intermediate network that includes a plurality of provider edge routing devices, wherein the information is received as one or more bridge protocol data units (BPDUs) containing spanning tree information associated with the loop detection protocol; and
a control unit that outputs a routing protocol message to communicate the BPDUs through the intermediate network via a routing protocol, wherein the routing protocol message includes the BPDUs as opaque data of the routing protocol message such that at least one routing device within the intermediate network ignores the opaque data when forwarding the routing protocol message,
wherein the control unit communicates the BPDUs such that a second L2 device associated with a second one of the L2 networks receiving the BPDUs can maintain spanning tree information that represents the plurality of L2 networks as a single comprehensive spanning tree in which the plurality of provider edge routing devices are represented as a single node,
wherein the intermediate network does not run the loop detection protocol between the provider edge routers of the intermediate network.
22. The device of claim 21, further comprising:
a virtual private LAN service (VPLS) module that forms a virtual network between the plurality of L2 networks; and
a module that executes an L2 loop detection protocol to detect loops within the virtual network in accordance with the L2 loop detection information.
23. The device of claim 21,
wherein the L2 loop detection information comprises spanning tree protocol (STP) information, and
wherein the device further comprises an STP module that, upon receiving the information, uses the L2 loop detection information to detect loops within an L2 network.
24. The device of claim 23, wherein the STP module analyzes the topology to detect any loops within the L2 device, and updates a status of one or more ports of the device upon detecting one or more loops.
25. The device of claim 21, wherein the control unit includes a border gateway protocol (BGP) module that communicates the L2 loop detection information via the BGP.
26. The device of claim 21, wherein the control unit receives the information from the plurality of L2 devices, selects a subset of the information received from the plurality of L2 devices, and communicates the selected subset information via the routing protocol to present the plurality of L2 devices as a single device.
27. The device of claim 21,
wherein the control unit stores topology data to reflect a topology of the first L2 network, and
wherein the control unit compares the L2 loop detection information with the topology data to determine whether a change to the topology has occurred, and selectively communicates loop detection information via the routing protocol based on the comparison.
28. The device of claim 21, wherein the control unit communicates the L2 loop detection information as information associated with a route advertised by the routing protocol message.
29. The device of claim 21, wherein the control unit communicates the L2 loop detection information as network layer reachability information (NLRI) associated with a route advertised by the routing protocol message.
30. The device of claim 21,
wherein the control unit receives the L2 loop detection information from an Ethernet bridge, and
wherein the control unit communicates the routing communication to a router via the routing protocol.
31. A provider edge routing device comprising:
a physical interface;
a routing module that receives loop detection information via a routing protocol message received on the physical interface, wherein the routing protocol message includes the information as opaque data of the routing protocol message such that at least one routing device within an intermediate network ignores the opaque data when forwarding the routing protocol message; and
a loop detection module that determines whether one or more loops exist within a network based on the received loop detection information, wherein the provider edge routing device does not run the loop detection protocol between other provider edge routers of the intermediate network.
32. The device of claim 31, wherein the loop detection module forwards the loop detection information to a layer two (L2) device in accordance with a loop detection protocol such that the L2 device can maintain spanning tree information that represents the plurality of L2 networks as a single comprehensive spanning tree in which the plurality of provider edge routing devices are represented as a single node.
33. The device of claim 32, further comprising:
a virtual private LAN service (VPLS) module that forms a virtual network between two or more L2 networks,
wherein the loop detection module updates L2 topology data based on the loop detection information to reflect a topology of the two or more L2 networks and the virtual network.
34. The device of claim 31, wherein the loop detection information comprises spanning tree protocol (STP) information.
35. The device of claim 31, wherein the loop detection module updates a status of one or more ports upon detecting one or more loops.
36. The device of claim 31, wherein the routing module comprises a border gateway protocol (BGP) module that receives the loop detection information via the BGP.
37. The device of claim 31, wherein the loop detection module generates one or more bridge protocol data units (BPDUs) containing the loop detection information, and sends the BPDUs to one or more L2 devices associated with an L2 network.
38. The device of claim 31, wherein the routing module receives the loop detection information with a route advertised by the routing protocol.
39. The device of claim 31, wherein the routing module receives the information as network layer reachability information (NLRI) associated with a route advertised by the routing protocol.
40. A non-transitory computer-readable medium comprising instructions for causing a programmable processor to:
execute a virtual private LAN service (VPLS) to form a virtual network between a first layer two (L2) network and a second L2 network coupled by an intermediate network;
receive spanning tree information from an L2 device of the first L2 network via the spanning tree protocol (STP), wherein the information is received as one or more bridge protocol data units (BPDUs) containing spanning tree information; and
communicate a routing protocol message that includes the spanning tree information through the intermediate network via provider edge routing device in accordance with a routing protocol to a routing device associated with the second L2 network, wherein the routing protocol message includes the BPDUs as opaque data of the routing protocol message such that at least one routing device within the intermediate network ignores the opaque data when forwarding the routing protocol message,
wherein the instructions to communicate comprises instructions to communicate the BPDUs such that a second L2 device associated with the second L2 network receiving the BPDUs can maintain spanning tree information that represents the L2 networks as a single comprehensive spanning tree in which the plurality of provider edge routing devices are represented as a single node,
wherein the intermediate network does not run the loop detection protocol between the provider edge routers of the intermediate network.
41. The computer-readable medium of claim 40, further comprising instructions for causing the programmable processor to:
maintain a topology for the first L2 network and second L2 network;
analyze the topology to detect any loops; and
selectively disable forwarding of network packets based on whether any loops are detected.
42. The computer-readable medium of claim 40, further comprising instructions for causing the programmable processor to:
maintain a topology for the first L2 network and second L2 network;
compare the spanning tree information with the topology to determine whether any changes to the topology have occurred; and
selectively communicate the spanning tree information via the routing protocol based on this comparison.
43. The computer-readable medium of claim 40, further comprising instructions for causing the programmable processor to communicate the spanning tree information via a Border Gateway Protocol (BGP) routing protocol message that contains the spanning tree information as network layer reachability information (NLRI) associated with an advertised route.
44. The computer-readable medium of claim 40, further comprising instructions for causing the programmable processor to receive the spanning tree information from the L2 device via bridge protocol data units (BPDUs) containing spanning tree information, wherein the L2 device comprises an Ethernet bridge, and wherein the provider edge routing device comprises an edge router associated with a service provider.
45. A non-transitory computer-readable medium comprising instructions for causing a programmable processor of a provider edge routing device to:
maintain routing information that represents a topology of a intermediate network;
forward packets in accordance with the routing information;
receive a routing communication via a routing protocol, wherein the routing communication comprises a routing protocol message that includes information associated with a layer two (L2) loop detection protocol, wherein the routing protocol message includes the information as opaque data of the routing protocol message such that at least one routing device within the intermediate network ignores the opaque data when forwarding the routing protocol message,
wherein the provider edge routing device does not run the loop detection protocol between other provider edge routers of the intermediate network; and
forward the information as one or more bridge protocol data units (BPDUs) containing the information associated with the loop detection protocol to an L2 device via the L2 loop detection protocol such that the L2 device can maintain spanning tree information that represents a plurality of L2 networks as a single comprehensive spanning tree in which a plurality of provider edge routing devices are represented as a single node.
46. The computer-readable medium of claim 45, further comprising instructions for causing a programmable processor to:
execute a virtual private LAN service (VPLS) to form a virtual network between a first L2 network and a second L2 network,
analyze the information to detect any loops within the first L2 and second L2 network, and
selectively disable the forwarding of at least some of the packets upon detecting one or more loops.
47. The computer-readable medium of claim 45, wherein the instructions cause the programmable processor to receive the information as network layer reachability information (NLRI) associated with an advertised route.
48. The computer-readable medium of claim 45, wherein the instructions cause the programmable processor to receive the information via the Border Gateway Protocol (BGP).