A liquid-crystal display device includes a pair of substrates, a liquid-crystal material layer sandwiched between the pair of substrates, and an optical compensation element having an optical compensation layer, the optical compensation layer including a stack group in which high-refractive-index obliquely deposited films and low-refractive-index obliquely deposited films are alternately deposited, the high-refractive-index obliquely deposited films and the low-refractive-index obliquely deposited films having a same tilt direction with respect to a normal line of a surface on which the films are deposited.

An optical film includes a polarizer. The polarizer includes a base layer, and a material of the base layer is obtained by dyeing a base material with a dye. The base material includes a polyvinyl alcohol material, and the dye is selected from blue dichroism organic dyes.

A composite lens system may include one or more first optical elements configured to provide a first focal length selected from a first continuous range of focal lengths, as well as one or more second optical elements configured to provide a discrete focal length selected from a plurality of discrete focal lengths. The one or more first optical elements and the one or more second optical elements may be configured in series such that the composite lens system provides an output focal length based on a combination of the selected first focal length and the selected discrete focal length.

In an electro-optical device, a first polarizing element, a first phase difference element, a transmissive liquid crystal panel, a second phase difference element, and a second polarizing element are sequentially arranged. Here, when a phase difference of the first phase difference element and the second phase difference element is λ/4, an influence of orientation disorder of liquid crystal molecules can be alleviated, but a contrast ratio is reduced. Therefore, when a wavelength of incident light is λ, a phase difference R of the first phase difference element and the second phase difference element satisfies the following condition that 0<R<λ/4, preferably λ/12<R<λ/6. For example, it is assumed that the phase difference R is λ/8.

In an electro-optical device, a first polarizing element, a first phase difference element, a transmissive liquid crystal panel, a second phase difference element, and a second polarizing element are sequentially arranged. Here, when a phase difference of the first phase difference element and the second phase difference element is λ/4, an influence of orientation disorder of liquid crystal molecules can be alleviated, but a contrast ratio is reduced. Therefore, when a wavelength of incident light is λ, a phase difference R of the first phase difference element and the second phase difference element satisfies the following condition that 0<R<λ/4, preferably λ/12<R<λ/6. For example, it is assumed that the phase difference R is λ/8.

A diffraction grating includes a substrate and a plurality of fringes supported by the substrate. The fringes run parallel to each other in a first direction. A refractive index of a material of the plurality of fringes is anisotropic, whereby a refractive index contrast of the diffraction grating depends on direction of electric field of an impinging light beam, and through that dependence is a function of an azimuthal angle of the impinging light beam. A dependence of the diffraction efficiency on the azimuthal angle is affected by the dependence of the refractive index contrast on the direction of electric field of an impinging light beam. A pupil-replicating waveguide may use such a diffraction grating as a coupler for in- our out-coupling image light.

A polarizing plate for IPS mode and an optical display apparatus including the same are provided. A polarizing plate includes: a polarizer; a first protective layer on an upper surface of the polarizer; and a second protective layer on a lower surface of the polarizer, wherein, assuming an axis of the polarizer having a high index of refraction in an in-plane direction of the polarizer is a reference axis (0°), an angle of an axis of the first protective layer having a low index of refraction in the in-plane direction thereof is in a range of about −5° to +5°, the first protective layer has an in-plane retardation Re of about 5,000 nm or more at a wavelength of 550 nm, the second protective layer includes a positive C plate layer, and the second protective layer satisfies at least one of Relations 1 and 2.

Provided are a bandpass filter having a high light transmittance in a transmission band and a wide wavelength range showing a high transmittance in the transmission band, and a sensor. The bandpass filter is a bandpass filter including a reflective member A and a reflective member B, in which a difference between a reflection center wavelength of the reflective member A and a reflection center wavelength of the reflective member B is larger than a sum of a half width at half maximum of a reflection band of the reflective member A and a half width at half maximum of a reflection band of the reflective member B; the reflective member A has a first cholesteric liquid crystal layer and a second cholesteric liquid crystal layer, and birefringence Δn1 of the first cholesteric liquid crystal layer is larger than birefringence Δn2 of the second cholesteric liquid crystal layer; and the reflective member B has a third cholesteric liquid crystal layer and a fourth cholesteric liquid crystal layer, and birefringence Δn3 of the third cholesteric liquid crystal layer is larger than birefringence Δn4 of the fourth cholesteric liquid crystal layer.

Provided are a bandpass filter having a high light transmittance in a transmission band and a wide wavelength range showing a high transmittance in the transmission band, and a sensor. The bandpass filter is a bandpass filter including a reflective member A and a reflective member B, in which a difference between a reflection center wavelength of the reflective member A and a reflection center wavelength of the reflective member B is larger than a sum of a half width at half maximum of a reflection band of the reflective member A and a half width at half maximum of a reflection band of the reflective member B; the reflective member A has a first cholesteric liquid crystal layer and a second cholesteric liquid crystal layer, and birefringence Δn1 of the first cholesteric liquid crystal layer is larger than birefringence Δn2 of the second cholesteric liquid crystal layer; and the reflective member B has a third cholesteric liquid crystal layer and a fourth cholesteric liquid crystal layer, and birefringence Δn3 of the third cholesteric liquid crystal layer is larger than birefringence Δn4 of the fourth cholesteric liquid crystal layer.

An object is to provide an optical system capable of improving the brightness of a main image while eliminating a ghost image. In an optical system including: an image display device that emits an image; a linear polarizer through which light associated with the image passes; a first quarter wavelength plate which receives the light from the linear polarizer; a half mirror; a reflective polarizer; and a second quarter wavelength plate provided between the reflective polarizer and the half mirror, retardance of the first quarter wavelength plate and retardance of the second quarter wavelength plate are equal, and thus the object is achieved.