Method of adjusting optical imaging system, positional deviation detecting mark, method of detecting positional deviation, method of detecting position, position detecting device and mark identifying device
A method of adjusting optical imaging system is provided to finely adjust arrangement of optical elements with sensitivity. Illumination light with a predetermined wavelength band is irradiated to an adjustment mark including first marks disposed at a first pitch and second marks disposed at a second pitch different from the first pitch. An image is captured according to light, of diffracted light emitted from the adjustment mark, passing through an aperture stop and reaching an image surface of the optical imaging system. A positional deviation between the first and second marks is calculated with symmetric/asymmetric property of luminance information. Based on respective positional deviations calculated while the wavelength band of illumination light is changed, arrangement of optical elements between a pupil plane and an aperture stop surface of the optical imaging system is finely adjusted, to correct imaging positional deviation of a pupil image on the aperture stop surface.
1. A method of adjusting an optical imaging system, comprising the steps of:
providing an object in the optical imaging system;
directing an epi-illumination light toward the object;
providing, on a surface of the object, a first mark and a second mark so that the first mark and the second mark are symmetric relative to a center of a visual field of the optical imaging system, the first mark being disposed at a first pitch which is equal to or more than a pitch such that first order diffracted beams in both a positive and negative direction in a predetermined wavelength band of the light can be located within a pupil area of the optical imaging system, the second mark being disposed at a second pitch which is smaller than the first pitch; and
adjusting a position of an optical element according to a relative position of an image of said first mark and an image of said second mark formed by said optical imaging system, the optical element being disposed between a pupil plane and an aperture stop surface of said optical imaging system,
wherein the following conditional equations are satisfied:
NAima>NAill
NAima−NAill>λ/P 1
NAima+NAill/ 2 ≦λ/P 2,
where said first pitch is P 1 (μm), said second pitch is P 2 (μm), numerical aperture of said optical imaging system is NAima, numerical aperture of an optical system used for irradiating said illumination light is Naill, and a central wavelength of said illumination light is λ (μm).
2. The method of adjusting an optical imaging system according to claim 1 , comprising the steps of:
measuring a distance between said first mark and said second mark in an image formed by said optical imaging system, before and after rotating said first and second marks by 180° relative to said center of the visual field,
calculating a tool induced shift amount from two measured distances and
adjusting the position of said optical element according to the calculated shift amount.
3. The method of adjusting an optical imaging system according to claim 1 , comprising the steps of:
obtaining, while changing a wavelength band of said illumination light, the relative position of the image of said first mark and the image of said second mark in each wavelength band, and
adjusting the position of said optical element according to the relative position obtained in each wavelength band.
4. The method of adjusting an optical imaging system according to claim 1 , wherein:
said optical element is a parallel flat plate; and
the position of said optical element is adjusted by tilting said parallel flat plate.
5. A method of adjusting an optical imaging system, comprising the steps of:
providing an object in the optical imaging system;
directing an epi-illumination light toward the object;
providing, on a surface of the object, a first mark and a second mark so that the first mark and the second mark are symmetric relative to a center of a visual field of the optical imaging system, the first mark being disposed at a first pitch which is equal to or more than a pitch such that first order diffracted beams in both a positive and negative direction in a predetermined wavelength band of the light can be located within a pupil area of the optical imaging system, the second mark being disposed at a second pitch which is smaller than the first pitch; and
adjusting a position of an optical element according to a relative position of an image of said first mark and an image of said second mark formed by said optical imaging system, the optical element being disposed between a pupil plane and an aperture stop surface of said optical imaging system;
obtaining, while changing a wavelength band of said illumination light, the relative position of the image of said first mark and the image of said second mark in each wavelength band;
adjusting the position of said optical element according to the relative position obtained in each wavelength band; and
adjusting the position of said optical element, using as an index a difference between distances between the image of said first mark and the image of said second mark calculated in each wavelength band of said illumination light, or a difference between tool induced shift amounts calculated in each wavelength band of said illumination light.