Phase shifted test pattern for monitoring focus and...

Optics: measuring and testing – Lens or reflective image former testing

Reexamination Certificate

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Reexamination Certificate

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06842237

ABSTRACT:
A method is described for determining lens aberrations using a test reticle and a standard metrology tool. The method provides test patterns, preferably in the form of standard overlay metrology test patterns, that include blazed gratings having orientation and pitch selected to sample desired portions of the lens pupil. The method measures relative shifts in the imaged test patterns using standard metrology tools to provide both magnitude and sign of the aberrations. The metrology tools need not be modified if standard test patterns are used, but can be adapted to obtain additional information. The test reticles may be formed with multiple test patterns having a range of orientations and pitch in order to compute any desired order of lens aberration. Alternatively, single test patterns may be used to determine both the magnitude and sign of lower order lens aberrations, such as defocus or coma.

REFERENCES:
patent: 5300786 (1994-04-01), Brunner et al.
patent: 5805290 (1998-09-01), Ausschnitt et al.
patent: 6091486 (2000-07-01), Kirk
patent: 6437858 (2002-08-01), Kouno et al.
patent: 6674511 (2004-01-01), Nomura et al.
SPIE 3697 -“Application of blazed gratings for determination of equivalent primary azimuthal aberrations” -Kirk and Progler -Proceedings SPIE, vol. 3679, pp. 70 -76, Date of Publication 1999, USA.
SPIE 4000 -“Impact of high order aberrations on the performance of the aberration monitor”-Dirksen et al.-Proceedings SPIE, vol. 4000, pp. 9 -17, Date of Publication 2000, USA.
SPIE 4000 -“In-situ measurement of lens aberrations” -Farrar et al.-Proceedings SPIE, vol. 4000, pp. 18 -29, Date of Publication 2000, USA.

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