1. A gear mounting having a spindle extending substantially normal to a carrier and capable of radial excursions from an initial position, when under load, characterised in that the spindle and carrier have generally frusto-conical abutment surfaces, normals to which extend substantially through the centroid of a projecting portion of the spindle and in that in the initial position of the spindle there is a gap between the abutment surfaces, said gap being sufficiently dimensioned to allow the spindle to be stressed in bending only up to a pre-determined load, such that when the pre-determined load is reached or exceeded, the abutment surfaces will engage to generate a reaction load whereby the spindle is stressed in tension and bending.
2. A gear mounting as claimed in claim 1 wherein the spindle is cantilevered from the carrier and includes radially inner and outer members and wherein the spindle abutment surface is on the outer member.
3. A gear mounting as claimed in claim 2 wherein, the inner member is a tension bolt.
4. A gear mounting as claimed in claim 1 wherein the carrier includes a ring or generally annular insert, which defines the abutment surface on the carrier.
5. A gear mounting as claimed in claim 3, wherein the tension bolt is surrounded by a sleeve.
6. A gear box including one or more gear mountings as claimed in claim 1.
7. A gear mounting having:
a spindle extending substantially normal to a carrier and capable of radial excursions from an initial position, when under load, characterised in that the spindle and carrier have generally frusto-conical abutment surfaces, normals to which extend substantially through the centroid of a projecting portion of the spindle, and in that in the initial position of the spindle there is a gap between the abutment surfaces, said gap configured to allow the spindle to be stressed in bending only up to a predetermined load;
wherein the abutment surfaces are configured to engage each other at or above the predetermined load to generate a reaction load whereby the spindle is stressed in tension and bending.
8. A gear mounting as claimed in claim 7, wherein the spindle is cantilevered from the carrier and includes radially inner and outer members and wherein the spindle abutment surface is on the outer member.
9. A gear mounting as claimed in claim 8, wherein the inner member is a tension bolt.
10. A gear mounting as claimed in claim 9, wherein the tension bolt is surrounded by a sleeve.
11. A gear mounting as claimed in claim 7, wherein the carrier includes a ring or generally annular insert, which defines the abutment surface on the carrier.
12. A gear box including one or more gear mountings as claimed in claim 7.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. An exposure apparatus comprising:
air pressure measurement means for measuring air pressure in a neighborhood of or inside a projection optical system;
first correction means, including aberration adjustment by driving a lens of the projection optical system, for repeatedly executing correction of an aberration based on the air pressure which is measured by said air pressure measurement means; and
second correction means, including aberration adjustment by changing a wavelength of an exposure light source, for executing correction of an aberration at a time interval longer than a repetition of the aberration correction executed by said first correction means, based on the air pressure which is measured by said air pressure measurement means.
2. The exposure apparatus according to claim 1, wherein said second correction means corrects more aberrations than that of the first correction means.
3. The exposure apparatus according to claim 1, wherein said first correction means performs correction at least during a shot of an exposure, and said second correction means performs correction in a non-shot state of the exposure.
4. The exposure apparatus according to claim 1, wherein said first correction means performs correction from the beginning of an exposure process for a wafer to the end of all shots of the exposure, and said second correction means performs correction while the wafer is exchanged after the end of said exposure process.
5. The exposure apparatus according to claim 1, wherein said second correction means performs aberration correction by changing the wavelength, or by changing the wavelength and driving the lens.
6. The exposure apparatus according to claim 1, further comprising stage driving means for adjusting an aberration by driving a wafer stage in the optical-axis direction,
wherein said first correction means and said second correction means performs aberration correction using said stage driving means.
7. The exposure apparatus according to claim 1, wherein said air pressure measurement means comprises:
a first barometer for detecting an absolute value of air pressure;
a second barometer for detecting an absolute value or a relative value of air pressure at higher speed than said first barometer; and
calibration means for calibrating an output of said second barometer based on an output of said first barometer, and outputting a calibration result as the measured air pressure value.
8. An exposure apparatus comprising:
a first barometer for detecting an absolute value of air pressure;
a second barometer for detecting an absolute value or a relative value of air pressure at higher speed than said first barometer;
calibration means for calibrating an output of said second barometer based on an output of said first barometer, and outputting a calibration result as a measured air pressure value; and
aberration correction means for performing aberration correction based on the air pressure value outputted by said calibration means.
9. The exposure apparatus according to claim 8, wherein said aberration correction means performs aberration correction by employing at least one of: aberration correction utilizing wavelength changing means which adjusts an aberration by changing a wavelength of an exposure light source, aberration correction utilizing lens driving means which adjusts an aberration by driving a lens of a projection optical system, and aberration correction utilizing stage driving means which adjusts an aberration by driving a wafer stage in an optical-axis direction.
10. The exposure apparatus according to claim 7, wherein said second barometer is configured with a laser interferometer.
11. An aberration correction method for correcting an aberration based on an air pressure value measured by air pressure measurement means that measures air pressure in a neighborhood of or inside a projection optical system, said method comprising:
a first correction step of repeatedly executing correction of a predetermined number of aberrations based on the air pressure value which is measured by the air pressure measurement means, said step including aberration adjustment by driving a lens of the projection optical system; and
a second correction step of executing aberration correction at a time interval longer than a repetition of the aberration correction executed in said first correction step, based on the air pressure which is measured by the air pressure measurement means, said step including aberration adjustment by changing a wavelength of an exposure light source.
12. A method of correcting an aberration caused by a change in air pressure in an exposure apparatus, comprising:
a calibration step of calibrating an output of a second barometer based on an output of a first barometer and outputting a calibration result as a measured air pressure value, said first barometer detecting an absolute value of air pressure and said second barometer detecting an absolute value or a relative value of air pressure at higher speed than the first barometer; and
an aberration correction step of performing aberration correction based on the air pressure value outputted in said calibration step.