Spectral image input device

A spectral image input device comprising:

• an image forming optical system for forming an image of image light on an image forming surface;
• a phase difference generating unit disposed anterior to the image forming surface in a direction of image light travel;
• and
• a first optical element disposed at an optically equivalent position with the image forming surface of the image forming optical system,
• the phase difference generating unit comprising sequentially in the direction of image light travel:
• a polarizer, a second optical element, and an analyzer,
• the polarizer for transmitting only polarized light in a specific direction;
• the second optical element formed of a solid material having a birefringence, and arranged such that a principal refraction index axis is inclined 45° relative to a polarization angle of the analyzer, the second optical element generating a phase difference in accordance with a wavelength of the image light based on a difference in a thickness of the second optical element in the direction of image light travel;
• and
• the analyzer for transmitting only the image light of a polarization angle of 90° relative to the direction of the polarized light of the polarizer;
• and
• wherein the difference in thickness at an optional transmission position of the second optical element satisfies the following equation:
• Δd=λ/(no−ne)
• where Δd represents the difference in thickness, λ represents the wavelength of the image light, no represents a refractive index of ordinary light transmitted through the second optical element, and ne represents a refractive index of extraordinary light transmitted through the second optical element.

A spectral image input device comprising:

• an image forming optical system for forming an image of image light on an image forming surface;
• a phase difference generating unit disposed anterior to the image forming surface in a direction of image light travel;
• and
• an area optical element disposed at an optically equivalent position with the image forming surface of the image forming optical system,
• the phase difference generating unit comprising sequentially in the direction of image light travel:
• a polarizer, a first optical element, and an analyzer,
• the polarizer for transmitting only polarized light in a specific direction;
• the first optical element formed of a solid material having a birefringence, and arranged such that a principal refraction index axis is inclined 45° relative to a polarization angle of the analyzer, the first optical element generating a phase difference in accordance with a wavelength of the image light based on a difference in a thickness of the first optical element in the direction of image light travel;
• the analyzer for transmitting only the image light of a polarization angle of 90° relative to the direction of the polarized light of the polarizer;
• and
• wherein the difference in thickness of the first optical element induces a phase difference in the image light only for a short wavelength component along a first edge, and induces a phase difference in the image light only for a long wavelength component along a second edge, such that the difference in thickness continuously changes from the first edge to the second edge.