Abstract: Four and five-layer antireflection coatings are disclosed suitable for use on optical parts such as lenses and prisms in which layers of thin films are formed on the surfaces of the optical parts by a process such as vacuum evaporation. By selecting the materials for the layers based on the refractive index of the materials, as well as based on the refractive index of the substrate, reflectance of the s-polarized component of incident light can be reduced over a large range of incident angle up to a range of approximately 45 degrees.

Abstract: A projector includes: imaging members producing primary color light images; an illumination optical system for illuminating the imaging members; an image combining optical system for combining the color light images; and a projection optical system for projecting a combined color light image onto a screen. The illumination optical system includes a beam splitter for splitting a visible light beam into two components having perpendicular polarization directions; a converter for making the polarization directions of the components coincide; and a color separator for separating light from the converter into rays of the plurality of primary colors. The beam splitter can have a first transparent base; a second transparent base; and a polarizing multilayered film placed between the first and second transparent bases.

Abstract: An optical device includes four prisms joined into one body to combine light beams, a first type of multilayer coating being provided between joining surfaces of the four prisms, and a second type of multilayer coating being provided on at least one non-joining surface of the four right-angle prisms. Each prism bears the first type of multilayer coating and the second type of multilayer coating on two or less surfaces thereof. The optical device is further provided with liquid crystal image panels to combine optical images and project a combined optical image to a screen.

Abstract: A beam splitter for use in a projector is provided with a first transparent base; a second transparent base; and a polarizing multilayered film placed between the first and second transparent bases. The polarizing multilayered film includes high refraction layers each having a refractive index n.sub.H and low refraction layers each having a refractive index n.sub.L lower than the refractive index n.sub.H the high refraction layers and the low refraction layers being alternately laminated one another. The refractive index n.sub.H and the refractive index n.sub.

Abstract: An anti-reflection coating with n layers on an optical part substrate made of synthetic resin wherein n is 3, 4, or 5, and the first layer at the air side comprises silicon dioxide (SiO.sub.2), and the n-th layer on the surface of the synthetic resin comprises ceric oxide (CeO.sub.2) is excellent in reflection reducing effect and does not result in the age-based change of the refractive index. And that the very good adhesion of the reflection reducing coating with the substrate results in hardness of layer stripping.Further an anti-reflection coating of the invention has reflection reducing effect in the near-infrared region.

Abstract: A multi-layered anti-reflection coating for use with a plastic substrate is provided. The coating consists of four layers and has high durability. The first layer furthest from the substrate is made of SiO.sub.2 ; the second layer is made of a mixture of ZrO.sub.2 and TiO.sub.2 ; the third layer is made of ZrO.sub.2 ; and the fourth layer is made of SiO or SiO.sub.2. The optical thicknesses of the first to third layers are about 0.25.lambda. with respect to a design wavelength .lambda., respectively. However the optical thickness of the fourth layer is greater than that of the respective first to third layers and selected between 0.5.lambda. to 2.0.lambda..

Abstract: A flame detector in which an infrared ray sensor having a specific infrared ray sensitivity and a visible ray sensor having a specific visible ray sensitivity are provided and output signals from both sensors are amplified by amplifiers, which in turn provide output signals to a phase discriminator circuit, the output signal from the amplifier for the infrared sensor output being also fed to a rectifier circuit for rectifying only a predetermined level or higher portion of the amplified output; an output signal from the rectifier circuit is fed to an integrator circuit and also fed to another integrator circuit through a switch which is opened when the output level of the phase discriminator circuit is "H"; then output signals from the integrator circuits are compared by a comparator and at the same time the output signal from said another integrator circuit is compared with a preset value by a comparator; and output signals from both comparators are fed to a control circuit which issues an alarm when the out

Abstract: A multi-layer anti-reflection coating is provided having four layers. The design can be defined by the following parameters:N.sub.1 d.sub.1 .congruent.0.25.lambda.o;N.sub.2 d.sub.2 .congruent.0.50.lambda.o;0.50.lambda.o.ltoreq.N.sub.3 d.sub.3 .ltoreq.0.75.lambda.o;N.sub.4 d.sub.4 <0.25.lambda.o;1.35.ltoreq.N.sub.1 .ltoreq.1.62;1.90.ltoreq.N.sub.2 .ltoreq.2.30;1.90.ltoreq.N.sub.4 .ltoreq.2.30;1.56.ltoreq.N.sub.3 .ltoreq.1.80; andN.sub.1 <N.sub.3wherein N refers to the refractive index, d refers to the physical thickness with their respective subnumbers referring to the layer, with the fourth layer being the layer closest to the substrate, and .lambda.o refers to a preselected design wavelength.