1. A lithographic projection apparatus, comprising:
an illumination system configured to provide a beam of radiation;
a support configured to support a patterning device, the patterning device being configured to pattern the beam of radiation, and the patterning device being provided with a reference alignment mark having a first period;
a substrate table configured to hold a substrate, the substrate being provided with a substrate overlay mark having a second period, the second period being smaller than the first period, the substrate being at least partially coated with a resist layer, the resist layer being provided with a resist overlay mark having a third period;
a projection system configured to project the patterned beam of radiation onto a target portion of the substrate; and
an alignment measuring system configured to measure overlay between the resist layer and the substrate by measuring an interference pattern that is generated by illuminating the substrate overlay mark and the resist overlay mark, the interference pattern having a fourth period that is larger than the second and third periods, and measuring alignment of a substrate alignment mark having a fifth period with respect to the reference alignment mark.
2. An apparatus method according to claim 1, wherein the substrate alignment mark has substantially the same period as the interference pattern, and the alignment measuring system is configured to image the substrate alignment mark on the reference alignment mark, and determine difference between positions of the image of the interference pattern and that of the substrate alignment mark with respect to the reference alignment mark.
3. An apparatus according to claim 1, wherein the substrate overlay mark, the resist overlay mark and the reference alignment mark are gratings.
4. An apparatus according to claim 1, wherein the resist overlay mark is a latent mark.
5. An apparatus according to claim 1, wherein the alignment measuring device is an on-axis alignment-measuring device, and the reference mark is a mask alignment mark.
6. An apparatus according to claim 1, wherein the interference pattern is imaged on the reference alignment mark via an optical filter, which selects diffraction orders of the radiation from the overlay marks which proceed to the reference alignment mark.
7. An apparatus according to claim 1, wherein the alignment measuring device is an off-axis alignment measuring device.
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. An identification medium which is observed via a linearly polarizing filter, comprising:
a first liquid crystal layer for changing a wavelength of light according to a rotational angle of the linearly polarizing filter;
a cholesteric liquid crystal layer; and
a light absorbing layer provided below the cholesteric liquid crystal layer.
2. The identification medium according to claim 1, wherein the first liquid crystal layer comprises at least one twisted nematic liquid crystal layer, in which a product by multiplying a birefringent value and a spiral pitch of liquid crystal molecules in the liquid crystal layer is greater than at least 3.5 times the wavelength of light having a wavelength of 400 nm to 800 nm and in which the selective reflection by Bragg diffraction is not caused, and a reflection layer.
3. The identification medium according to claim 1, wherein an arrangement pattern of the first liquid crystal layer and an arrangement pattern of the cholesteric liquid crystal layer are provided at the same side.
4. The identification medium according to claim 1, further comprising:
a layer in which a gap is formed.
5. The identification medium according to claim 1, further comprising:
an ink layer in which the color changes by temperature.
6. The identification medium according to claim 1,
wherein the cholesteric liquid crystal layer includes two or more cholesteric liquid crystal layers having different optical characteristic, and
wherein the two or more cholesteric liquid crystal layers have an optical characteristic that light having at least one of different wavelength and different turning direction is reflected.
7. The identification medium according to claim 1, further comprising:
a color shift film having a structure laminating two or more light passing films in which refractive indexes of the adjoining light passing films are different.
8. The identification medium according to claim 1, further comprising:
a hologram layer in which a hologram is formed.
9. The identification medium according to claim 1, further comprising:
a fluorescent ink layer.
10. The identification medium according to claim 1, further comprising:
a nematic liquid crystal layer for forming a latent image, wherein the nematic liquid crystal layer acts as a wavelength plate having a phase difference or distributed phase differences in the range of n+(\xbd) to n+(\xbc) times the wavelength which is used for the identification (n is a natural number including 0).
11. An identification method, comprising:
a first photographing step for photographing the identification medium according to claim 1 via an identification filter in which a linearly polarizing plate and a quarter-wavelength plate are laminated and in which one side faces toward the identification medium;
a second photographing step for photographing the identification medium via the identification filter in which the other side faces toward the identification medium; and
a judging step for determining authenticity of the identification medium by using an image obtained in at least one of the first photographing step and the second photographing step.
12. An identification apparatus, comprising:
at least one identification filter laminating a linearly polarizing plate and a quarter-wavelength plate;
a first photographing apparatus for photographing the identification medium according to claim 1 via the identification filter in which one side faces toward the identification medium;
a second photographing apparatus for photographing the identification medium via the identification filter in which the other side faces toward the identification medium; and
a judging means for determining authenticity of the identification medium by using an image that was photographed by at least one of the first photographing apparatus and the second photographing apparatus.