Optical system and device using the same
First Claim
1. An optical system which is disposed between an image plane and an optical pupil and having generally positive power, wherein:
- said optical system comprises a first prism having a refractive index of greater than 1, a second prism having a refracting index of greater than 1, and a volume hologram element disposed between said first prism and said second prism and cemented thereto, wherein;
said volume hologram element comprises a first grating vector corresponding to at least a first wavelength and a second grating vector corresponding to a second wavelength shorter than said first wavelength, said volume hologram element is designed in such a way that diffraction efficiency thereof reaches a maximum at a first angle of incidence and a first angle of reflection and diffraction which vary with the position of said volume hologram element at at least said first wavelength and at a second angle of incidence and a second angle of reflection and diffraction which vary with the position of said volume hologram element at at least said second wavelength, said first prism is located on said optical pupil side and said second prism is located on said image plane side, said second prism has at least one reflecting surface formed at a surface thereof different from a surface thereof facing said volume hologram element, a light beam, which propagates from said optical pupil to said image plane in a forward or backward direction and includes at least a ray component of said first wavelength and at least a ray component of said second wavelength, passes through said volume hologram element in order from said first prism side to said second prism side, whereupon said light beam is reflected at said reflecting surface in said second prism and reflected and diffracted by said volume hologram element in said second prism, a first λ
θ
continuous curve region is defined by a region in an angle-wavelength space, at which the diffraction efficiency is 10% or greater, as determined from the refractive index of a medium of said second prism, the average refractive index of a medium of said volume hologram element, the amplitude of a refractive index modulation of the medium of said volume hologram element, the thickness of said volume hologram element, said first angle of incidence, said first angle of reflection and diffraction and said first grating vector, a second λ
θ
continuous curve region is defined by a region in an angle-wavelength space, at which the diffraction efficiency is 10% or greater, as determined from the refractive index of the medium of said second prism, the average refractive index of the medium of said volume hologram element, the amplitude of the refractive index modulation of the medium of said volume hologram element, the thickness of said volume hologram element, said second angle of incidence, said second angle of reflection and diffraction and said second grating vector, and said light beam is designed in such a way that upon passing through said volume hologram element, said ray component of said first wavelength transmits at an angle of incidence in a region between said first λ
θ
continuous curve region and said second λ
θ
continuous curve region and said ray component of said second wavelength transmits at an angle of incidence in a region on a shorter wavelength side with respect to said second λ
θ
continuous curve region.
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Accused Products
Abstract
The invention relates to a viewing and an image pickup optical system for display devices, which can be used with high efficiency at a plurality of wavelengths and enables bright images to be viewed with satisfactory color reproducibility. The optical system comprises a first prism 3, a second prism 4 and a volume hologram element 6 disposed between them and cemented to them. The hologram element 6 comprises a first grating vector corresponding to at least a first wavelength and a second grating vector corresponding to a second wavelength shorter than the first wavelength. As the light beam comprising the first and second wavelengths passes through the hologram element 6, the component of the first wavelength transmits at a given angle of incidence in a region between a first λθ continuous curved region in which the diffraction efficiency is 10% or greater as determined form the first grating vector and a second λθ continuous curved region in which the diffraction efficiency is 10% or greater as determined from the second grating vector, and the component of the second wavelength transmits at a given angle of incidence in a region on a shorter wavelength side with respect to the 2 λθ continuous curved region.
9 Citations
20 Claims
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1. An optical system which is disposed between an image plane and an optical pupil and having generally positive power, wherein:
said optical system comprises a first prism having a refractive index of greater than 1, a second prism having a refracting index of greater than 1, and a volume hologram element disposed between said first prism and said second prism and cemented thereto, wherein;
said volume hologram element comprises a first grating vector corresponding to at least a first wavelength and a second grating vector corresponding to a second wavelength shorter than said first wavelength, said volume hologram element is designed in such a way that diffraction efficiency thereof reaches a maximum at a first angle of incidence and a first angle of reflection and diffraction which vary with the position of said volume hologram element at at least said first wavelength and at a second angle of incidence and a second angle of reflection and diffraction which vary with the position of said volume hologram element at at least said second wavelength, said first prism is located on said optical pupil side and said second prism is located on said image plane side, said second prism has at least one reflecting surface formed at a surface thereof different from a surface thereof facing said volume hologram element, a light beam, which propagates from said optical pupil to said image plane in a forward or backward direction and includes at least a ray component of said first wavelength and at least a ray component of said second wavelength, passes through said volume hologram element in order from said first prism side to said second prism side, whereupon said light beam is reflected at said reflecting surface in said second prism and reflected and diffracted by said volume hologram element in said second prism, a first λ
θ
continuous curve region is defined by a region in an angle-wavelength space, at which the diffraction efficiency is 10% or greater, as determined from the refractive index of a medium of said second prism, the average refractive index of a medium of said volume hologram element, the amplitude of a refractive index modulation of the medium of said volume hologram element, the thickness of said volume hologram element, said first angle of incidence, said first angle of reflection and diffraction and said first grating vector,a second λ
θ
continuous curve region is defined by a region in an angle-wavelength space, at which the diffraction efficiency is 10% or greater, as determined from the refractive index of the medium of said second prism, the average refractive index of the medium of said volume hologram element, the amplitude of the refractive index modulation of the medium of said volume hologram element, the thickness of said volume hologram element, said second angle of incidence, said second angle of reflection and diffraction and said second grating vector, andsaid light beam is designed in such a way that upon passing through said volume hologram element, said ray component of said first wavelength transmits at an angle of incidence in a region between said first λ
θ
continuous curve region and said second λ
θ
continuous curve region and said ray component of said second wavelength transmits at an angle of incidence in a region on a shorter wavelength side with respect to said second λ
θ
continuous curve region.- View Dependent Claims (3, 4, 5, 6, 7, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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2. An optical system which is disposed between an image plane and an optical pupil and having generally positive power, wherein:
said optical system comprises a first prism having a refractive index of greater than 1, a second prism having a refracting index of greater than 1, and a volume hologram element disposed between said first prism and said second prism and cemented thereto, wherein;
said volume hologram element comprises a first grating vector corresponding to at least a first wavelength and a second grating vector corresponding to a second wavelength shorter than said first wavelength, said volume hologram element is designed in such a way that diffraction efficiency thereof reaches a maximum at a first angle of incidence and a first angle of reflection and diffraction which vary with the position of said volume hologram element at at least said first wavelength and at a second angle of incidence and a second angle of reflection and diffraction which vary with the position of said volume hologram element at at least said second wavelength, said first prism is located on said optical pupil side and said second prism is located on said image plane side, said second prism has at least one reflecting surface formed at a surface thereof different from a surface thereof facing said volume hologram element, a light beam, which propagates from said optical pupil to said image plane in a forward or backward direction and includes at least a ray component of said first wavelength and at least a ray component of said second wavelength, passes through said volume hologram element in order from said first prism side to said second prism side, whereupon said light beam is reflected at said reflecting surface in said second prism and reflected and diffracted by said volume hologram element in said second prism, a first λ
θ
continuous curve region is defined by a region in an angle-wavelength space, at which the diffraction efficiency is 10% or greater, as determined from the refractive index of a medium of said second prism, the average refractive index of a medium of said volume hologram element, the amplitude of a refractive index modulation of the medium of said volume hologram element, the thickness of said volume hologram element, said first angle of incidence, said first angle of reflection and diffraction and said first grating vector,a second λ
θ
continuous curve region is defined by a region in an angle-wavelength space, at which the diffraction efficiency is 10% or greater, as determined from the refractive index of the medium of said second prism, the average refractive index of the medium of said volume hologram element, the amplitude of the refractive index modulation of the medium of said volume hologram element, the thickness of said volume hologram element, said second angle of incidence, said second angle of reflection and diffraction and said second grating vector, andsaid light beam is designed in such a way that upon passing through said volume hologram element, both said ray components of said first wavelength and said second wavelength transmit at an angle of incidence in a region on a shorter wavelength side with respect to said second λ
θ
continuous curve region.
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8. The optical system according to clam 6, wherein a ghost light removal member for preventing ghost light from striking on the eyeball of an observer is provided on an optically inactive surface of said first and second prisms other than optically active surfaces for transmitting and reflecting light rays.
Specification