Optical device having a light emitter and a photosensor on the same optical axis

摘要

An optical device structure can be simplified and miniaturized on the whole. A fabrication of optical device can be simplified and the optical device can be improved in reliability. The optical device can increase its output, operate a light emitting light source with a reduced power and reduce a power consumption by increasing a quantity of reflected-back light to a photosensor device, i.e., a quantity of photosensed light. An optical device includes a light emitting section (1), a radiated section (2), a converging means (3) and a photosensor section (4). Light emitted from the light emitting section (1) is converged and radiated on the radiated section (2) by the converging means (3). Reflected-back light (LR) reflected from the radiated section (2) is converged and the photosensor section (4) is disposed near a confocal of the converging means (3) concerning reflected-back light from the radiated section (2). Light emitted from the light emitting section (1) is passed through a path of the same axis and photosensed by the photosensor section (4) as shown by a one-dot chain line (a) representing the optical axis before and after the emitted light is reflected by the radiated section (2).