Abstract: An inspection apparatus for inspecting printed circuit boards on which components have been mounted, wherein a light source that generates a light beam in a concentrated spot fashion is mounted on a rotary object and radiates the beam spot onto the printed circuit board at approximately right angles thereto while the rotary object is rotating, so that the surface of the printed circuit board is scanned by the beam spot. Changes of at least either one of the reflection angle and the intensity of the light reflected from the printed circuit board is detected by photoelectric converters provided on the rotary object, and at least either one of the height and the brightness of the position at which the beam spot and the printed circuit board are intersected is measured, thereby performing the inspection of the printed circuit board.

Abstract: In a plate microlens of the invention wherein gradient index lenses each having an optical axis along a normal to a surface of a transparent base and a refractive index profile gradually changing along a direction of the optical axis and a direction perpendicular thereto are formed integrally in the transparent base, a ratio d/a (where d is a thickness of the gradient index lens on the optical axis and 2a is a diameter of the gradient index lens on a surface of the transparent base) falls within a range of 0.46 to 0.78.

Abstract: An optical waveguide device of the invention has an optical waveguide which is a region formed in a transparent substrate and has a refractive index higher than that of the transparent substrate. The optical waveguide consists of first and second optical waveguide elements each having one end exposed to a surface of the transparent substrate and the other end connected in the vinicity of the surface of the transparent substrate, such that the connecting portion thereof is exposed to the surface of the transparent substrate.

Abstract: A plate lens comprising a transparent base having two flat surfaces and having a plano-convex lens portion which is formed integrally with the transparent base, which has a refractive index greater than that of the transparent base and which has a substantially semicircular or circular section in a direction perpendicular to the flat surfaces of the transparent base. The plate lens has a light-shielding layer on one surface of the transparent base, as needed. The light-shielding layer covers one surface of the transparent base such that a transparent portion may be formed in the vicinity of a position opposing the central point or line of the plano-convex lens portion. The plate lens provides a clear and bright image and is therefore applicable to faceplates for various types of display devices, CRTs and the like. The plate lens may be mass-produced at low cost.