1. A measuring apparatus comprising:
a first mask having a pinhole for generating a spherical wave as measuring light;
a second mask provided subsequent to said first mask in a light traveling direction, said second mask having two pairs of selecting windows that allow the measuring light that has passed a target optical system to transmit through the selecting windows; and
a two-dimensional light divider, located between said first and second masks, for two-dimensionally dividing incident light into two pairs of \xb11st order lights,
wherein the two pairs of selecting windows in the second mask are arranged at a position where each of the two pairs of \xb11st order lights passes through simultaneously and
wherein said measuring apparatus calculates optical performance of the target optical system from an interference fringe formed by a shearing interference between each measuring light that has passed the selecting windows.
2. A measuring apparatus according to claim 1, wherein the optical performance is a wave front aberration.
3. A measuring apparatus according to claim 1, wherein said measuring apparatus calculates the optical performance from wave front aberration of the target optical system with respect to two orthogonal directions, and
wherein the two pairs of selecting windows in the second mask allow \xb11st order diffracted lights of the measuring light in the two orthogonal directions to simultaneously pass through the two pairs of selecting windows.
4. An exposure apparatus for exposing a pattern on a mask onto an object using light, said exposure apparatus comprising:
a projection optical system for projecting the pattern onto the object; and
a measuring apparatus according to claim 1 for detecting a wave front aberration of the projection optical system.
5. An exposure apparatus according to claim 4, wherein the light has a wavelength of 20 nm or less.
6. A device manufacturing method comprising the steps of:
exposing an object to be exposed using an exposure apparatus; and
developing the exposed object,
wherein said exposure apparatus includes:
a projection optical system for projecting the pattern onto the object; and
a measuring apparatus according to claim 1 for detecting a wave front aberration of the projection optical system.
7. A measuring apparatus according to claim 1, wherein each measuring light that has passed the two pairs of selecting windows has information regarding wave front aberration of the target optical system.
8. A measuring apparatus according to claim 1, wherein said measuring apparatus calculates the optical performance of the target optical system by Fourier-transforming the interference fringe.
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 of selecting a channel for wireless audiovisual (AV) equipment, comprising:
establishing a monitoring channel set, the monitoring channel set including at least one channel operable by the AV equipment;
establishing an operation mode as a station mode;
scanning each channel of the monitoring channel set to obtain information;
computing a parameter based upon the obtained information for each channel;
selecting a channel with optimized condition from operable channels by comparing parameters of each channel; and
forming a wireless network using the selected channel by converting the operation mode to an Access Point (AP) modes,
wherein the parameter computed by the AV equipment is computed for the at least one operable channel,
wherein the parameter includes at least one of a parameter distance, which is a distance on a frequency between the computed channel and an interference channel nearest the computed channel;
a parameter numBSS_adj, which is a number of external wireless networks within an adjacent channel scope having influence on the computed channel;
a parameter numBSS_adj_legacy, which is a number of external wireless networks of a legacy standard within an adjacent channel scope having influence on the computed channel;
a parameter interferers_loc, which is a position of an interference channel relative to the computed channel;
a parameter numBSS_nearest, which is a number of external wireless networks located at an interference channel nearest to the computed channel;
a parameter maxRSSI_nearest, which is a maximum value of signal strengths detected by a channel computed by the external wireless networks; and
a first center frequency which is a center frequency of a channel to be computed.
2. The method as recited in claim 1, wherein the wireless network is a wireless LAN.
3. The method as recited in claim 1, wherein the monitoring channel set further comprises:
a channel straddled with the at least one operable channel wherein the straddled channel is not the operable channel.
4. The method as recited in claim 1, wherein scanning each channel comprises active scanning, the active scanning being configured for a wireless communication network conforming to a communication standard of the AV equipment.
5. The method as recited in claim 4, wherein the operation of scanning comprises passive scanning, the passive scanning being configured for a wireless communication network which conforms to a communication standard different from the AV equipment communication standard.
6. The method as recited in claim 1, wherein the detected noise information includes a wireless noise signal strength of the scanned channel.
7. The method as recited in claim 1, wherein the parameter distance is a smaller value of a first difference between the first center frequency and a second center frequency and a second difference between the first center frequency and a third center frequency, wherein the second center frequency is a largest frequency among center frequencies that are smaller than the first center frequency out of a channel in which noise or an external wireless network operating in a space is detected, and wherein the third frequency a smallest frequency among frequencies that are equal to or larger than the first center frequency out of a channel in which noise or an external wireless network operate.
8. The method as recited in claim 7, wherein the second center frequency is denoted by a value of \u2212\u221e and the third center frequency is denoted by a value of \u221e when the external wireless network and noise are not detected.
9. The method as recited in claim 1, wherein an adjacent channel scope of the parameter numBSS_adj comprises a channel in which a signal size is maintained on the computed channel by a spectrum mask of a wireless LAN.
10. The method as recited in claim 1, wherein an adjacent channel scope of the parameter numBSS_adj_legacy comprises a channel in which a signal size is maintained on the computed channel computed by a spectrum mask of a wireless LAN.
11. The method as recited in claim 1, wherein the parameter interferers loc is classified into three states comprising a first state that includes no detection of external wireless or noise in any channel of the monitoring-channel set; a second state where the detected center frequency of the interference channel is a value smaller or larger than the first center frequency; and a third state configured for cases that are different and not classifiable in at least one of the first state and the second state.
12. The method as recited in claim 1, wherein the parameter maxRSSI nearest is the maximum value among signal strength values of signals detected on the computed channels by the external wireless network, the signal strength values being based on an attenuation pre-set in response to a distance from the center frequency of the computed channel.
13. The method as recited in claim 12, wherein the attenuation includes attenuation associated with a wireless LAN spectrum mask established for each external wireless network.
14. The method as recited in claim 1, wherein priority of a high discrimination standard for the parameters is given in an order of the parameter distance, the parameter numBSS_adj, the parameter numBSS_adj_legacy, the parameter interferers_loc, the parameter numBSS_nearest, the parameter maxRSSI_nearest and the first center frequency.
15. The method as recited in claim 14, wherein the AV equipment compares values of a parameter of each operable channel having the next highest priority in order to select the optimum channel when the optimum channel is not selected through a comparison of the parameter of each operable channel having the highest priority.
16. The method as recited in claim 1, wherein the channel states of the parameter numBSS_adj, the parameter numBSS_adj_legacy, the parameter numBSS_nearest, the parameter maxRSSI_nearest and the first center frequency are discriminated as satisfactory if the values are small with respect to other values corresponding to each parameter, while the channel state of the parameter distance is discriminated as satisfactory if the value is large with respect to other values of parameter distance.
17. A method of selecting a channel for wireless audiovisual (AV) equipment comprising:
establishing a monitoring channel set, the monitoring channel set including at least one channel operable by the AV equipment;
scanning channels of the monitoring channel set to obtain information,
wherein the monitoring channel set is established by a station mode;
computing a parameter from the obtained information for the channels of the monitoring channel set;
comparing parameters of the channels thereby selecting a channel with optimized condition from operable channels of the channels; and
converting the operation mode to an Access Point (AP) mode and forming a wireless network using the selected channel,
wherein the parameter is computed for at least one operable channel,
and the parameter comprises at least one of a parameter distance, which is a distance on a frequency between the computed channel and an interference channel nearest the computed channel;
a parameter numBSS_adj, which is a number of external wireless networks within an adjacent channel scope having influence on the computed channel;
a parameter numBSS_adj_legacy, which is a number of external wireless networks of a legacy standard within an adjacent channel scope having influence on the computed channel;
a parameter interferers_loc, which is a position of an interference channel relative to the computed channel;
a parameter numBSS_nearest, which is a number of external wireless networks located at an interference channel nearest to the computed channel;
a parameter maxRSSI_nearest, which is a maximum value among signal strengths detected by a channel computed by the external wireless networks;
and a first center frequency, which is a center frequency to be computed.